Search Discussions

Adam Danz
Last activity 2024-5-30

How to leave feedback for documentation pages

How to leave feedback on a doc page

Leaving feedback is a two-step process. At the bottom of most pages in the MATLAB documentation is a star rating.

Start by selecting a star that best answers the question. After selecting a star rating, an edit box appears where you can offer specific feedback.

When you press "Submit" you'll see the confirmation dialog below. You cannot go back and edit your content, although you can refresh the page to go through that process again.

Tips on leaving feedback

Be productive. The reader should clearly understand what action you'd like to see, what was unclear, what you think needs work, or what areas were really helpful.
Positive feedback is also helpful. By nature, feedback often focuses on suggestions for changes but it also helps to know what was clear and what worked well.
Point to specific areas of the page. This helps the reader to narrow the focus of the page to the area described by your feedback.

What happens to that feedback?

Before working at MathWorks I often left feedback on documentation pages but I never knew what happens after that. One day in 2021 I shared my speculation on the process:

> That feedback is received by MathWorks Gnomes which are never seen nor heard but visit the MathWorks documentation team at night while they are sleeping and whisper selected suggestions into their ears to manipulate their dreams. Occassionally this causes them to wake up with a Eureka moment that leads to changes in the documentation.

I'd like to let you in on the secret which is much less fanciful. Feedback left in the star rating and edit box are collected and periodically reviewed by the doc writers who look for trends on highly trafficked pages and finer grain feedback on less visited pages. Your feedback is important and often results in improvements.

David
Last activity 2024-5-23

Introduced in...

A colleague said that you can search the Help Center using the phrase 'Introduced in' followed by a release version. Such as, 'Introduced in R2022a'. Doing this yeilds search results specific for that release.

Seems pretty handy so I thought I'd share.

Chen Lin
Last activity 2024-5-22

Celebrating Spring: MATLAB Tulip

Bringing the beauty of MathWorks Natick's tulips to life through code!

Get the code from @Eric Ludlam.

Remix challenge: create and share with us your new breeds of MATLAB tulips!

Mathew
Last activity 2024-5-16

Any helpful link

is there any sites available online free ai course learning except: coursera.org

Chen Lin
Last activity 2024-7-3

Northern Lights

Northern lights captured from this weekend at MathWorks campus ✨

Did you get a chance to see lights and take some photos?

Robert
Last activity 2024-5-13

Alpha Vantage: Easy tutorial on how to get data into Matlab from Alpha Vantage

From Alpha Vantage's website: API Documentation | Alpha Vantage

Try using the built-in Matlab function webread(URL)... for example:

% copy a URL from the examples on the site
URL = 'https://www.alphavantage.co/query?function=TIME_SERIES_DAILY&symbol=IBM&apikey=demo'
% or use the pattern to create one
tickers = [{'IBM'} {'SPY'} {'DJI'} {'QQQ'}]; i = 1;
URL = ...
['https://www.alphavantage.co/query?function=TIME_SERIES_DAILY_ADJUSTED&outputsize=full&symbol=', ...
        + tickers{i}, ...
        + '&apikey=***Put Your API Key here***'];
X = webread(URL);

You can access any of the data available on the site as per the Alpha Vantage documentation using these two lines of code but with different designations for the requested data as per the documentation.

It's fun!

https://www.mathworks.com/matlabcentral/fileexchange/165846-matlab-plot-cheat-sheet

Zhaoxu Liu / slandarer
Last activity 2024-5-13

Latest version of MATLAB-PLOT-CHEAT-SHEET

This cheat sheet is here:

reference:

MATLAB used to have official visualization-cheat-sheet, but there have been quite a few new updates in MATLAB versions recently. Therefore, I made my own cheat sheet and marked the versions of each new thing that were released :

Mike
Last activity 2024-5-31

Research ethics using generative A.I

Dear members, I’m currently doing research on the subject of using Generative A.I. as a digital designer. What our research group would like to know is which ethical issues have a big impact on the decisions you guys and girls make using generative A.I.

Whether you’re using A.I. or not, we would really like to know your vision and opinion about this subject. Please empty your thoughts and oppinion into your answers, we would like to get as much information as possible.

Are you currently using A.I. when doing your job? Yes, what for. No (not yet), why not?

Using A.I., would you use real information or alter names/numbers to get an answer?

What information would or wouldn’t you use? If the client is asking/ordering you to do certain things that go against your principles, would you still do it because order is order? How far would you go?

Who is responsible for the outcome of the generated content, you or the client?

Would you still feel like a product owner if it was co-developed with A.I.?

What we are looking for is that we would like to know why people do or don’t use AI in the field of design and wich ethical considerations they make. We’re just looking for general moral line of people, for example: 70% of designers don’t feel owner of a design that is generated by AI but 95% feels owner when it is co-created.

So therefore the questions we asked, we want to know the how you feel about this.

Adam Danz
Last activity 2024-4-22

Debugging Using Conditional Breakpoints & fprintf

Temporary print statements are often helpful during debugging but it's easy to forget to remove the statements or sometimes you may not have writing privileges for the file. This tip uses conditional breakpoints to add print statements without ever editing the file!

What are conditional breakpoints?

Conditional breakpoints allow you to write a conditional statement that is executed when the selected line is hit and if the condition returns true, MATLAB pauses at that line. Otherwise, it continues.

The Hack: use ~fprintf() as the condition

fprintf prints information to the command window and returns the size of the message in bytes. The message size will always be greater than 0 which will always evaluate as true when converted to logical. Therefore, by negating an fprintf statement within a conditional breakpoint, the fprintf command will execute, print to the command window, and evalute as false which means the execution will continue uninterupted!

How to set a conditional break point

1. Right click the line number where you want the condition to be evaluated and select "Set Conditional Breakpoint"

2. Enter a valid MATLAB expression that returns a logical scalar value in the editor dialog.

Handy one-liners

Check if a line is reached: Don't forget the negation (~) and the line break (\n)!

~fprintf('Entered callback function\n')

Display the call stack from the break point line: one of my favorites!

~fprintf('%s\n',formattedDisplayText(struct2table(dbstack)))

Inspect variable values: For scalar values,

~fprintf('v = %.5f\n', v)

Use formattedDisplayText to convert more complex data to a string

~fprintf('%s\n', formattedDisplayText(v)).

Make sense of frequent hits: In some situations such as responses to listeners or interactive callbacks, a line can be executed 100s of times per second. Incorporate a timestamp to differentiate messages during rapid execution.

~fprintf('WindowButtonDownFcn - %s\n', datetime('now'))

Closing

This tip not only keeps your code clean but also offers a dynamic way to monitor code execution and variable states without permanent modifications. Interested in digging deeper? @Steve Eddins takes this tip to the next level with his Code Trace for MATLAB tool available on the File Exchange (read more).

Summary animation

To reproduce the events in this animation:

% buttonDownFcnDemo.m
fig = figure();
tcl = tiledlayout(4,4,'TileSpacing','compact');
for i = 1:16
    ax = nexttile(tcl); 
    title(ax,"#"+string(i))
    ax.ButtonDownFcn = @axesButtonDownFcn;
    xlim(ax,[-1 1])
    ylim(ax,[-1,1])
    hold(ax,'on')
end
function axesButtonDownFcn(obj,event)
    colors = lines(16); 
    plot(obj,event.IntersectionPoint(1),event.IntersectionPoint(2),...
        'ko','MarkerFaceColor',colors(obj.Layout.Tile,:))
end

https://sherwood.news/tech/how-do-ai-models-stack-up-vs-humans-on-standardized-benchmarks/

David
Last activity 2024-4-18

AI Models Are Improving Every Year

How long until the 'dumbest' models are smarter than your average person? Thanks for sharing this article @Adam Danz

Athanasios Paraskevopoulos
Last activity 2024-7-27

Seeking Contributors for Upcoming Book on Matrix Algebra with MATLAB for Undergraduate Students

Hello MathWorks Community,

I am excited to announce that I am currently working on a book project centered around Matrix Algebra, specifically designed for MATLAB users. This book aims to cater to undergraduate students in engineering, where Matrix Algebra serves as a foundational element.

Matrix Algebra is not only pivotal in understanding complex engineering concepts but also in applying these principles effectively in various technological solutions. MATLAB, renowned for its powerful computational capabilities, is an excellent tool to explore and implement these concepts, making it a perfect companion for this book.

As I embark on this journey to create a resource that bridges theoretical matrix algebra with practical MATLAB applications, I am looking for one or two knowledgeable individuals who have a firm grasp of both subjects. If you have experience in teaching or applying matrix algebra in engineering contexts and are familiar with MATLAB, your contribution could be invaluable.

Collaborators will help in shaping the content to ensure it is educational, engaging, and technically robust, making complex concepts accessible and applicable for students.

If you are interested in contributing to this project or know someone who might be, please reach out to discuss how we can work together to make this book a valuable resource for engineering students.

Thank you and looking forward to your participation!

Zhaoxu Liu / slandarer
Last activity 2024-4-11

These Pretty Chord Diagrams Were All Made By MATLAB???

The beautiful and elegant chord diagrams were all created using MATLAB?

Indeed, they were all generated using the chord diagram plotting toolkit that I developed myself:

- Chord chart: [chord chart](https://www.mathworks.com/matlabcentral/fileexchange/116550-chord-chart)
- Directed graph chord chart: [digraph chord chart]:(https://www.mathworks.com/matlabcentral/fileexchange/121043-digraph-chord-chart)

You can download these toolkits from the provided links.

The reason for writing this article is that many people have started using the chord diagram plotting toolkit that I developed. However, some users are unsure about customizing certain styles. As the developer, I have a good understanding of the implementation principles of the toolkit and can apply it flexibly. This has sparked the idea of challenging myself to create various styles of chord diagrams. Currently, the existing code is quite lengthy. In the future, I may integrate some of this code into the toolkit, enabling users to achieve the effects of many lines of code with just a few lines.

Without further ado, let's see the extent to which this MATLAB toolkit can currently perform.

demo 1

rng(2)
dataMat = randi([0,5], [11,5]);
dataMat(1:6,1) = 0;
dataMat([11,7],1) = [45,25];
dataMat([1,4,5,7],2) = [20,20,30,30];
dataMat(:,3) = 0;
dataMat(6,3) = 45;
dataMat(1:5,4) = 0;
dataMat([6,7],4) = [25,25];
dataMat([5,6,9],5) = [25,25,25];
colName = {'Fly', 'Beetle', 'Leaf', 'Soil', 'Waxberry'};
rowName = {'Bartomella', 'Bradyrhizobium', 'Dysgomonas', 'Enterococcus',...
           'Lactococcus', 'norank', 'others', 'Pseudomonas', 'uncultured',...
           'Vibrionimonas', 'Wolbachia'};
figure('Units','normalized', 'Position',[.02,.05,.6,.85])
CC = chordChart(dataMat, 'rowName',rowName, 'colName',colName, 'Sep',1/80);
CC = CC.draw();
% 修改上方方块颜色(Modify the color of the blocks above)
CListT = [0.7765 0.8118 0.5216; 0.4431 0.4706 0.3843; 0.5804 0.2275 0.4549;
          0.4471 0.4039 0.6745; 0.0157 0      0     ];
for i = 1:size(dataMat, 2)
    CC.setSquareT_N(i, 'FaceColor',CListT(i,:))
end
% 修改下方方块颜色(Modify the color of the blocks below)
CListF = [0.5843 0.6863 0.7843; 0.1098 0.1647 0.3255; 0.0902 0.1608 0.5373;
          0.6314 0.7961 0.2118; 0.0392 0.2078 0.1059; 0.0157 0      0     ;
          0.8549 0.9294 0.8745; 0.3882 0.3255 0.4078; 0.5020 0.7216 0.3843;
          0.0902 0.1843 0.1804; 0.8196 0.2314 0.0706];
for i = 1:size(dataMat, 1)
    CC.setSquareF_N(i, 'FaceColor',CListF(i,:))
end
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        CC.setChordMN(i,j, 'FaceColor',CListT(j,:), 'FaceAlpha',.5)
    end
end
CC.tickState('on')
CC.labelRotate('on')
CC.setFont('FontSize',17, 'FontName','Cambria')
% CC.labelRotate('off')
% textHdl = findobj(gca,'Tag','ChordLabel');
% for i = 1:length(textHdl)
%     if textHdl(i).Position(2) < 0
%         if abs(textHdl(i).Position(1)) > .7
%             textHdl(i).Rotation = textHdl(i).Rotation + 45;
%             textHdl(i).HorizontalAlignment = 'right';
%             if textHdl(i).Rotation > 90
%                 textHdl(i).Rotation = textHdl(i).Rotation + 180;
%                 textHdl(i).HorizontalAlignment = 'left';
%             end
%         else
%             textHdl(i).Rotation = textHdl(i).Rotation + 10;
%             textHdl(i).HorizontalAlignment = 'right';
%         end
%     end
% end

demo 2

rng(3)
dataMat = randi([1,15], [7,22]);
dataMat(dataMat < 11) = 0;
dataMat(1, sum(dataMat, 1) == 0) = 15;
colName = {'A2M', 'FGA', 'FGB', 'FGG', 'F11', 'KLKB1', 'SERPINE1', 'VWF',...
           'THBD', 'TFPI', 'PLAT', 'SERPINA5', 'SERPIND1', 'F2', 'PLG', 'F12',...
           'SERPINC1', 'SERPINA1', 'PROS1', 'SERPINF2', 'F13A1', 'PROC'};
rowName = {'Lung', 'Spleen', 'Liver', 'Heart',...
           'Renal cortex', 'Renal medulla', 'Thyroid'};
figure('Units','normalized', 'Position',[.02,.05,.6,.85])
CC = chordChart(dataMat, 'rowName',rowName, 'colName',colName, 'Sep',1/80, 'LRadius',1.21);
CC = CC.draw();
CC.labelRotate('on')
% 单独设置每一个弦末端方块(Set individual end blocks for each chord)
% Use obj.setEachSquareF_Prop 
% or  obj.setEachSquareT_Prop
% F means from (blocks below)
% T means to   (blocks above)
CListT = [173,70,65; 79,135,136]./255;
% Upregulated:1 | Downregulated:2
Regulated = rand([7, 22]);
Regulated = (Regulated < .8) + 1;
for i = 1:size(Regulated, 1)
    for j = 1:size(Regulated, 2)
        CC.setEachSquareT_Prop(i, j, 'FaceColor', CListT(Regulated(i,j),:))
    end
end
% 绘制图例(Draw legend)
H1 = fill([0,1,0] + 100, [1,0,1] + 100, CListT(1,:), 'EdgeColor','none');
H2 = fill([0,1,0] + 100, [1,0,1] + 100, CListT(2,:), 'EdgeColor','none');
lgdHdl = legend([H1,H2], {'Upregulated','Downregulated'}, 'AutoUpdate','off', 'Location','best');
lgdHdl.ItemTokenSize = [12,12];
lgdHdl.Box = 'off';
lgdHdl.FontSize = 13;
% 修改下方方块颜色(Modify the color of the blocks below)
CListF = [128,108,171; 222,208,161; 180,196,229; 209,150,146; 175,201,166;
          134,156,118; 175,175,173]./255;
for i = 1:size(dataMat, 1)
    CC.setSquareF_N(i, 'FaceColor',CListF(i,:))
end
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        CC.setChordMN(i,j, 'FaceColor',CListF(i,:), 'FaceAlpha',.45)
    end
end

demo 3

dataMat = rand([15,15]);
dataMat(dataMat > .15) = 0;
CList = [ 75,146,241; 252,180, 65; 224, 64, 10;   5,100,146; 191,191,191;
          26, 59,105; 255,227,130;  18,156,221; 202,107, 75;   0, 92,219;
         243,210,136;  80, 99,129; 241,185,168; 224,131, 10; 120,147,190]./255;
figure('Units','normalized', 'Position',[.02,.05,.6,.85])
BCC = biChordChart(dataMat, 'Arrow','on', 'CData',CList);
BCC = BCC.draw();
% 添加刻度
BCC.tickState('on')
% 修改字体，字号及颜色
BCC.setFont('FontName','Cambria', 'FontSize',17, 'Color',[0,0,.8])

demo 4

rng(5)
dataMat = randi([1,20], [5,5]);
dataMat(1,1) = 110;
dataMat(2,2) = 40;
dataMat(3,3) = 50;
dataMat(5,5) = 50;
CList1 = [164,190,158; 216,213,153; 177,192,208; 238,238,227; 249,217,153]./255;
CList2 = [247,204,138; 128,187,185; 245,135,124; 140,199,197; 252,223,164]./255;
CList = CList2;
NameList={'CHORD','CHART','MADE','BY','SLANDARER'};
figure('Units','normalized', 'Position',[.02,.05,.6,.85])
BCC = biChordChart(dataMat, 'Arrow','on', 'CData',CList, 'Sep',1/30, 'Label',NameList, 'LRadius',1.33);
BCC = BCC.draw();
% 添加刻度
BCC.tickState('on')
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        if dataMat(i,j) > 0
            BCC.setChordMN(i,j, 'FaceAlpha',.7, 'EdgeColor',CList(i,:)./1.1)
        end
    end
end
% 修改方块颜色(Modify the color of the blocks)
for i = 1:size(dataMat, 1)
    BCC.setSquareN(i, 'EdgeColor',CList(i,:)./1.7)
end
% 修改字体，字号及颜色
BCC.setFont('FontName','Cambria', 'FontSize',17)
BCC.tickLabelState('on')
BCC.setTickFont('FontName','Cambria', 'FontSize',9)

demo 5

dataMat=randi([1,20], [14,3]);
dataMat(11:14,1) = 0;
dataMat(6:10,2) = 0;
dataMat(1:5,3) = 0;
colName =  compose('C%d', 1:3);
rowName = [compose('A%d', 1:7), compose('B%d', 7:-1:1)];
figure('Units','normalized', 'Position',[.02,.05,.6,.85])
CC = chordChart(dataMat, 'rowName',rowName, 'colName',colName, 'Sep',1/80);
CC = CC.draw();
% 修改上方方块颜色(Modify the color of the blocks above)
for i = 1:size(dataMat, 2)
    CC.setSquareT_N(i, 'FaceColor',[190,190,190]./255)
end
% 修改下方方块颜色(Modify the color of the blocks below)
CListF=[255,244,138; 253,220,117; 254,179, 78; 253,190, 61;
        252, 78, 41; 228, 26, 26; 178,  0, 36;   4, 84,119;
          1,113,137;  21,150,155;  67,176,173;  68,173,158;
        123,204,163; 184,229,162]./255;
for i = 1:size(dataMat, 1)
    CC.setSquareF_N(i, 'FaceColor',CListF(i,:))
end
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        CC.setChordMN(i,j, 'FaceColor',CListF(i,:), 'FaceAlpha',.5)
    end
end
CC.tickState('on')
CC.tickLabelState('on')

demo 6

rng(2)
dataMat = randi([0,40], [20,4]);
dataMat(rand([20,4]) < .2) = 0;
dataMat(1,3) = 500;
dataMat(20,1:4) = [140; 150; 80; 90];
colName = compose('T%d', 1:4);
rowName = compose('SL%d', 1:20);
figure('Units','normalized', 'Position',[.02,.05,.6,.85])
CC = chordChart(dataMat, 'rowName',rowName, 'colName',colName, 'Sep',1/80, 'LRadius',1.23);
CC = CC.draw();
% 修改上方方块颜色(Modify the color of the blocks above)
CListT = [0.62,0.49,0.27; 0.28,0.57,0.76
          0.25,0.53,0.30; 0.86,0.48,0.34];
for i = 1:size(dataMat, 2)
    CC.setSquareT_N(i, 'FaceColor',CListT(i,:))
end
% 修改下方方块颜色(Modify the color of the blocks below)
CListF = [0.94,0.84,0.60; 0.16,0.50,0.67; 0.92,0.62,0.49;
    0.48,0.44,0.60; 0.48,0.44,0.60; 0.71,0.79,0.73;
    0.96,0.98,0.98; 0.51,0.82,0.95; 0.98,0.70,0.82;
    0.97,0.85,0.84; 0.55,0.64,0.62; 0.94,0.93,0.60;
    0.98,0.90,0.85; 0.72,0.84,0.81; 0.85,0.45,0.49;
    0.76,0.76,0.84; 0.59,0.64,0.62; 0.62,0.14,0.15;
    0.75,0.75,0.75; 1.00,1.00,1.00];
for i = 1:size(dataMat, 1)
    CC.setSquareF_N(i, 'FaceColor',CListF(i,:))
end
CC.setSquareF_N(size(dataMat, 1), 'EdgeColor','k', 'LineWidth',1)
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        CC.setChordMN(i,j, 'FaceColor',CListT(j,:), 'FaceAlpha',.46)
    end
end
CC.tickState('on')
CC.labelRotate('on')
CC.setFont('FontSize',17, 'FontName','Cambria')

demo 7

dataMat = randi([10,10000], [10,10]);
dataMat(6:10,:) = 0;
dataMat(:,1:5) = 0;
NameList = {'BOC', 'ICBC', 'ABC', 'BOCM', 'CCB', ...
            'yama', 'nikoto', 'saki', 'koto', 'kawa'};
CList = [0.63,0.75,0.88
    0.67,0.84,0.75
    0.85,0.78,0.88
    1.00,0.92,0.93
    0.92,0.63,0.64
    0.57,0.67,0.75
    1.00,0.65,0.44
    0.72,0.73,0.40
    0.65,0.57,0.58
    0.92,0.94,0.96];
figure('Units','normalized', 'Position',[.02,.05,.6,.85])
BCC = biChordChart(dataMat, 'Arrow','on', 'CData',CList, 'Label',NameList);
BCC = BCC.draw();
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        if dataMat(i,j) > 0
            BCC.setChordMN(i,j, 'FaceAlpha',.85, 'EdgeColor',CList(i,:)./1.5, 'LineWidth',.8)
        end
    end
end
for i = 1:size(dataMat, 1)
    BCC.setSquareN(i, 'EdgeColor',CList(i,:)./1.5, 'LineWidth',1)
end
% 添加刻度、修改字体
BCC.tickState('on')
BCC.setFont('FontName','Cambria', 'FontSize',17)

demo 8

dataMat = rand([11,4]);
dataMat = round(10.*dataMat.*((11:-1:1).'+1))./10;
colName = {'A','B','C','D'};
rowName = {'Acidobacteriota', 'Actinobacteriota', 'Proteobacteria', ...
           'Chloroflexi', 'Bacteroidota', 'Firmicutes', 'Gemmatimonadota', ...
           'Verrucomicrobiota', 'Patescibacteria', 'Planctomyetota', 'Others'};
figure('Units','normalized', 'Position',[.02,.05,.8,.85])
CC = chordChart(dataMat, 'colName',colName, 'Sep',1/80, 'SSqRatio',30/100);% -30/100
CC = CC.draw();
% 修改上方方块颜色(Modify the color of the blocks above)
CListT = [0.93,0.60,0.62
    0.55,0.80,0.99
    0.95,0.82,0.18
    1.00,0.81,0.91];
for i = 1:size(dataMat, 2)
    CC.setSquareT_N(i, 'FaceColor',CListT(i,:))
end
% 修改下方方块颜色(Modify the color of the blocks below)
CListF = [0.75,0.73,0.86
    0.56,0.83,0.78
    0.00,0.60,0.20
    1.00,0.49,0.02
    0.78,0.77,0.95
    0.59,0.24,0.36
    0.98,0.51,0.45
    0.96,0.55,0.75
    0.47,0.71,0.84
    0.65,0.35,0.16
    0.40,0.00,0.64];
for i = 1:size(dataMat, 1)
    CC.setSquareF_N(i, 'FaceColor',CListF(i,:))
end
% 修改弦颜色(Modify chord color)
CListC = [0.55,0.83,0.76
    0.75,0.73,0.86
    0.00,0.60,0.19
    1.00,0.51,0.04];
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        CC.setChordMN(i,j, 'FaceColor',CListC(j,:), 'FaceAlpha',.4)
    end
end
% 单独设置每一个弦末端方块(Set individual end blocks for each chord)
% Use obj.setEachSquareF_Prop 
% or  obj.setEachSquareT_Prop
% F means from (blocks below)
% T means to   (blocks above)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        CC.setEachSquareT_Prop(i,j, 'FaceColor', CListF(i,:))
    end
end
% 添加刻度
CC.tickState('on')
% 修改字体，字号及颜色
CC.setFont('FontName','Cambria', 'FontSize',17)
% 隐藏下方标签
textHdl = findobj(gca, 'Tag','ChordLabel');
for i = 1:length(textHdl)
    if textHdl(i).Position(2) < 0
        set(textHdl(i), 'Visible','off')
    end
end
% 绘制图例(Draw legend)
scatterHdl = scatter(10.*ones(size(dataMat,1)),10.*ones(size(dataMat,1)), ...
                     55, 'filled');
for i = 1:length(scatterHdl)
    scatterHdl(i).CData = CListF(i,:);
end
lgdHdl = legend(scatterHdl, rowName, 'Location','best', 'FontSize',16, 'FontName','Cambria', 'Box','off');
set(lgdHdl, 'Position',[.7482,.3577,.1658,.3254])

demo 9

dataMat = randi([0,10], [5,5]);
CList1 = [0.70,0.59,0.67
    0.62,0.70,0.62
    0.81,0.75,0.62
    0.80,0.62,0.56
    0.62,0.65,0.65];
CList2 = [0.02,0.02,0.02
    0.59,0.26,0.33
    0.38,0.49,0.38
    0.03,0.05,0.03
    0.29,0.28,0.32];
CList = CList2;
NameList={'CHORD','CHART','MADE','BY','SLANDARER'};
figure('Units','normalized', 'Position',[.02,.05,.6,.85])
BCC = biChordChart(dataMat, 'Arrow','on', 'CData',CList, 'Sep',1/30, 'Label',NameList, 'LRadius',1.33);
BCC = BCC.draw();
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        BCC.setChordMN(i,j, 'FaceAlpha',.5)
    end
end
% 修改方块颜色(Modify the color of the blocks)
for i = 1:size(dataMat, 1)
    BCC.setSquareN(i, 'EdgeColor',[0,0,0], 'LineWidth',5)
end
% 添加刻度
BCC.tickState('on')
% 修改字体，字号及颜色
BCC.setFont('FontSize',17, 'FontWeight','bold')
BCC.tickLabelState('on')
BCC.setTickFont('FontSize',9)

demo 10

rng(2)
dataMat = rand([14,5]) > .3;
colName = {'phosphorylation', 'vasculature development', 'blood vessel development', ...
           'cell adhesion', 'plasma membrane'};
rowName = {'THY1', 'FGF2', 'MAP2K1', 'CDH2', 'HBEGF', 'CXCR4', 'ECSCR',...
           'ACVRL1', 'RECK', 'PNPLA6', 'CDH5', 'AMOT', 'EFNB2', 'CAV1'};
figure('Units','normalized', 'Position',[.02,.05,.9,.85])
CC = chordChart(dataMat, 'colName',colName, 'rowName',rowName, 'Sep',1/80, 'LRadius',1.2);
CC = CC.draw();
% 修改上方方块颜色(Modify the color of the blocks above)
CListT1 = [0.5686    0.1961    0.2275
    0.2275    0.2863    0.3765
    0.8431    0.7882    0.4118
    0.4275    0.4510    0.2706
    0.3333    0.2706    0.2510];
CListT2 = [0.4941    0.5490    0.4118
    0.9059    0.6510    0.3333
    0.8980    0.6157    0.4980
    0.8902    0.5137    0.4667
    0.4275    0.2824    0.2784];
CListT3 = [0.4745    0.5843    0.7569
    0.4824    0.5490    0.5843
    0.6549    0.7216    0.6510
    0.9412    0.9216    0.9059
    0.9804    0.7608    0.6863];
CListT = CListT3;
for i = 1:size(dataMat, 2)
    CC.setSquareT_N(i, 'FaceColor',CListT(i,:), 'EdgeColor',[0,0,0])
end
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        CC.setChordMN(i,j, 'FaceColor',CListT(j,:), 'FaceAlpha',.9, 'EdgeColor',[0,0,0])
    end
end
% 修改下方方块颜色(Modify the color of the blocks below)
logFC = sort(rand(1,14))*6 - 3;
for i = 1:size(dataMat, 1)
    CC.setSquareF_N(i, 'CData',logFC(i), 'FaceColor','flat', 'EdgeColor',[0,0,0])
end
CMap = [     0         0    1.0000; 0.0645    0.0645    1.0000; 0.1290    0.1290    1.0000; 0.1935    0.1935    1.0000
        0.2581    0.2581    1.0000; 0.3226    0.3226    1.0000; 0.3871    0.3871    1.0000; 0.4516    0.4516    1.0000
        0.5161    0.5161    1.0000; 0.5806    0.5806    1.0000; 0.6452    0.6452    1.0000; 0.7097    0.7097    1.0000
        0.7742    0.7742    1.0000; 0.8387    0.8387    1.0000; 0.9032    0.9032    1.0000; 0.9677    0.9677    1.0000
        1.0000    0.9677    0.9677; 1.0000    0.9032    0.9032; 1.0000    0.8387    0.8387; 1.0000    0.7742    0.7742
        1.0000    0.7097    0.7097; 1.0000    0.6452    0.6452; 1.0000    0.5806    0.5806; 1.0000    0.5161    0.5161
        1.0000    0.4516    0.4516; 1.0000    0.3871    0.3871; 1.0000    0.3226    0.3226; 1.0000    0.2581    0.2581
        1.0000    0.1935    0.1935; 1.0000    0.1290    0.1290; 1.0000    0.0645    0.0645; 1.0000         0         0];
colormap(CMap);
try clim([-3,3]),catch,end
try caxis([-3,3]),catch,end
CBHdl = colorbar();
CBHdl.Position = [0.74,0.25,0.02,0.2];
% =========================================================================
% 交换XY轴(Swap XY axis)
patchHdl = findobj(gca, 'Type','patch');
for i = 1:length(patchHdl)
    tX = patchHdl(i).XData;
    tY = patchHdl(i).YData;
    patchHdl(i).XData = tY;
    patchHdl(i).YData = - tX;
end
txtHdl = findobj(gca, 'Type','text');
for i = 1:length(txtHdl)
    txtHdl(i).Position([1,2]) = [1,-1].*txtHdl(i).Position([2,1]);
    if txtHdl(i).Position(1) < 0
        txtHdl(i).HorizontalAlignment = 'right';
    else
        txtHdl(i).HorizontalAlignment = 'left';
    end
end
lineHdl = findobj(gca, 'Type','line');
for i = 1:length(lineHdl)
    tX = lineHdl(i).XData;
    tY = lineHdl(i).YData;
    lineHdl(i).XData = tY;
    lineHdl(i).YData = - tX;
end
% =========================================================================
txtHdl = findobj(gca, 'Type','text');
for i = 1:length(txtHdl)
    if txtHdl(i).Position(1) > 0
        txtHdl(i).Visible = 'off';
    end
end
text(1.25,-.15, 'LogFC', 'FontSize',16)
text(1.25,1, 'Terms', 'FontSize',16)
patchHdl = [];
for i = 1:size(dataMat, 2)
    patchHdl(i) = fill([10,11,12],[10,13,13], CListT(i,:), 'EdgeColor',[0,0,0]);
end
lgdHdl = legend(patchHdl, colName, 'Location','best', 'FontSize',14, 'FontName','Cambria', 'Box','off');
lgdHdl.Position = [.735,.53,.167,.27];
lgdHdl.ItemTokenSize = [18,8];

demo 11

rng(2)
dataMat = rand([12,12]);
dataMat(dataMat < .85) = 0;
dataMat(7,:) = 1.*(rand(1,12)+.1);
dataMat(11,:) = .6.*(rand(1,12)+.1);
dataMat(12,:) = [2.*(rand(1,10)+.1), 0, 0];
CList = [repmat([49,49,49],[10,1]); 235,28,34; 19,146,241]./255;
figure('Units','normalized', 'Position',[.02,.05,.6,.85])
BCC = biChordChart(dataMat, 'Arrow','off', 'CData',CList);
BCC = BCC.draw();
% 添加刻度
BCC.tickState('on')
% 修改字体，字号及颜色
BCC.setFont('FontName','Cambria', 'FontSize',17)
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        if dataMat(i,j) > 0
            BCC.setChordMN(i,j, 'FaceAlpha',.78, 'EdgeColor',[0,0,0])
        end
    end
end
% 修改方块颜色(Modify the color of the blocks)
for i = 1:size(dataMat, 1)
    BCC.setSquareN(i, 'EdgeColor',[0,0,0], 'LineWidth',2)
end

demo 12

dataMat = rand([9,9]);
dataMat(dataMat > .7) = 0;
dataMat(eye(9) == 1) = (rand([1,9])+.2).*3;
CList = [0.85,0.23,0.24
0.96,0.39,0.18
0.98,0.63,0.22
0.99,0.80,0.26
0.70,0.76,0.21
0.24,0.74,0.71
0.27,0.65,0.84
0.09,0.37,0.80
0.64,0.40,0.84];
figure('Units','normalized', 'Position',[.02,.05,.6,.85])
BCC = biChordChart(dataMat, 'Arrow','on', 'CData',CList);
BCC = BCC.draw();
% 添加刻度、刻度标签
BCC.tickState('on')
% 修改字体，字号及颜色
BCC.setFont('FontName','Cambria', 'FontSize',17)
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        if dataMat(i,j) > 0
            BCC.setChordMN(i,j, 'FaceAlpha',.7)
        end
    end
end

demo 13

rng(2)
dataMat = randi([1,40], [7,4]);
dataMat(rand([7,4]) < .1) = 0;
colName = compose('MATLAB%d', 1:4);
rowName = compose('SL%d', 1:7);
figure('Units','normalized', 'Position',[.02,.05,.7,.85])
CC = chordChart(dataMat, 'rowName',rowName, 'colName',colName, 'Sep',1/80, 'LRadius',1.32);
CC = CC.draw();
% 修改上方方块颜色(Modify the color of the blocks above)
CListT = [0.49,0.64,0.53
    0.75,0.39,0.35
    0.80,0.74,0.42
    0.40,0.55,0.66];
for i = 1:size(dataMat, 2)
    CC.setSquareT_N(i, 'FaceColor',CListT(i,:))
end
% 修改下方方块颜色(Modify the color of the blocks below)
CListF = [0.91,0.91,0.97
    0.62,0.95,0.66
    0.91,0.61,0.20
    0.54,0.45,0.82
    0.99,0.76,0.81
    0.91,0.85,0.83
    0.53,0.42,0.43];
for i = 1:size(dataMat, 1)
    CC.setSquareF_N(i, 'FaceColor',CListF(i,:))
end
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        CC.setChordMN(i,j, 'FaceColor',CListT(j,:), 'FaceAlpha',.46)
    end
end
CC.tickState('on')
CC.tickLabelState('on')
CC.setFont('FontSize',17, 'FontName','Cambria')
CC.setTickFont('FontSize',8, 'FontName','Cambria')
% 绘制图例(Draw legend)
scatterHdl = scatter(10.*ones(size(dataMat,1)),10.*ones(size(dataMat,1)), ...
                     55, 'filled');
for i = 1:length(scatterHdl)
    scatterHdl(i).CData = CListF(i,:);
end
lgdHdl = legend(scatterHdl, rowName, 'Location','best', 'FontSize',16, 'FontName','Cambria', 'Box','off');
set(lgdHdl, 'Position',[.77,.38,.1658,.27])

demo 14

rng(6)
dataMat = randi([1,20], [8,8]);
dataMat(dataMat > 5) = 0;
dataMat(1,:) = randi([1,15], [1,8]);
dataMat(1,8) = 40;
dataMat(8,8) = 60;
dataMat = dataMat./sum(sum(dataMat));
CList = [0.33,0.53,0.86
    0.94,0.50,0.42
    0.92,0.58,0.30
    0.59,0.47,0.45
    0.37,0.76,0.82
    0.82,0.68,0.29
    0.75,0.62,0.87
    0.43,0.69,0.57];
NameList={'CHORD', 'CHART', 'AND', 'BICHORD',...
    'CHART', 'MADE', 'BY', 'SLANDARER'};
figure('Units','normalized', 'Position',[.02,.05,.6,.85])
BCC = biChordChart(dataMat, 'Arrow','on', 'CData',CList, 'Sep',1/12, 'Label',NameList, 'LRadius',1.33);
BCC = BCC.draw();
% 添加刻度
BCC.tickState('on')
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        if dataMat(i,j) > 0
            BCC.setChordMN(i,j, 'FaceAlpha',.7, 'EdgeColor',CList(i,:)./1.1)
        end
    end
end
% 修改方块颜色(Modify the color of the blocks)
for i = 1:size(dataMat, 1)
    BCC.setSquareN(i, 'EdgeColor',CList(i,:)./1.7)
end
% 修改字体，字号及颜色
BCC.setFont('FontName','Cambria', 'FontSize',17)
BCC.tickLabelState('on')
BCC.setTickFont('FontName','Cambria', 'FontSize',9)
% 调整数值字符串格式
% Adjust numeric string format
BCC.setTickLabelFormat(@(x)[num2str(round(x*100)),'%'])

demo 15

CList = [0.81,0.72,0.83
0.69,0.82,0.89
0.17,0.44,0.64
0.70,0.85,0.55
0.03,0.57,0.13
0.97,0.67,0.64
0.84,0.09,0.12
1.00,0.80,0.46
0.98,0.52,0.01
    ];
figure('Units','normalized', 'Position',[.02,.05,.53,.85], 'Color',[1,1,1])
% =========================================================================
ax1 = axes('Parent',gcf, 'Position',[0,1/2,1/2,1/2]);
dataMat = rand([9,9]);
dataMat(dataMat > .4) = 0;
BCC = biChordChart(dataMat, 'Arrow','on', 'CData',CList);
BCC = BCC.draw();
BCC.tickState('on')
BCC.setFont('Visible','off')
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        if dataMat(i,j) > 0
            BCC.setChordMN(i,j, 'FaceAlpha',.6)
        end
    end
end
text(-1.2,1.2, 'a', 'FontName','Times New Roman', 'FontSize',35)
% =========================================================================
ax2 = axes('Parent',gcf, 'Position',[1/2,1/2,1/2,1/2]);
dataMat = rand([9,9]);
dataMat(dataMat > .4) = 0;
dataMat = dataMat.*(1:9);
BCC = biChordChart(dataMat, 'Arrow','on', 'CData',CList);
BCC = BCC.draw();
BCC.tickState('on')
BCC.setFont('Visible','off')
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        if dataMat(i,j) > 0
            BCC.setChordMN(i,j, 'FaceAlpha',.6)
        end
    end
end
text(-1.2,1.2, 'b', 'FontName','Times New Roman', 'FontSize',35)
% =========================================================================
ax3 = axes('Parent',gcf, 'Position',[0,0,1/2,1/2]);
dataMat = rand([9,9]);
dataMat(dataMat > .4) = 0;
dataMat = dataMat.*(1:9).';
BCC = biChordChart(dataMat, 'Arrow','on', 'CData',CList);
BCC = BCC.draw();
BCC.tickState('on')
BCC.setFont('Visible','off')
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        if dataMat(i,j) > 0
            BCC.setChordMN(i,j, 'FaceAlpha',.6)
        end
    end
end
text(-1.2,1.2, 'c', 'FontName','Times New Roman', 'FontSize',35)
% =========================================================================
ax4 = axes('Parent',gcf, 'Position',[1/2,0,1/2,1/2]);
ax4.XColor = 'none'; ax4.YColor = 'none';
ax4.XLim = [-1,1]; ax4.YLim = [-1,1];
hold on
NameList = {'Food supply', 'Biodiversity', 'Water quality regulation', ...
            'Air quality regulation', 'Erosion control', 'Carbon storage', ...
            'Water retention', 'Recreation', 'Soil quality regulation'};
patchHdl = [];
for i = 1:size(dataMat, 2)
    patchHdl(i) = fill([10,11,12],[10,13,13], CList(i,:), 'EdgeColor',[0,0,0]);
end
lgdHdl = legend(patchHdl, NameList, 'Location','best', 'FontSize',14, 'FontName','Cambria', 'Box','off');
lgdHdl.Position = [.625,.11,.255,.27];
lgdHdl.ItemTokenSize = [18,8];

demo 16

dataMat = rand([15,15]);
dataMat(dataMat > .2) = 0;
CList = [ 75,146,241; 252,180, 65; 224, 64, 10;   5,100,146; 191,191,191;
          26, 59,105; 255,227,130;  18,156,221; 202,107, 75;   0, 92,219;
         243,210,136;  80, 99,129; 241,185,168; 224,131, 10; 120,147,190]./255;
CListC = [54,69,92]./255;
CList = CList.*.6 + CListC.*.4;
figure('Units','normalized', 'Position',[.02,.05,.6,.85])
BCC = biChordChart(dataMat, 'Arrow','on', 'CData',CList);
BCC = BCC.draw();
% 添加刻度
BCC.tickState('on')
% 修改字体，字号及颜色
BCC.setFont('FontName','Cambria', 'FontSize',17, 'Color',[0,0,0])
% 修改弦颜色(Modify chord color)
for i = 1:size(dataMat, 1)
    for j = 1:size(dataMat, 2)
        if dataMat(i,j) > 0
            BCC.setChordMN(i,j, 'FaceColor',CListC ,'FaceAlpha',.07)
        end
    end
end
[~, N] = max(sum(dataMat > 0, 2));
for j = 1:size(dataMat, 2)
    BCC.setChordMN(N,j, 'FaceColor',CList(N,:) ,'FaceAlpha',.6)
end

You need to download following tools:

- Chord chart: [chord chart](https://www.mathworks.com/matlabcentral/fileexchange/116550-chord-chart)
- Directed graph chord chart: [digraph chord chart]:(https://www.mathworks.com/matlabcentral/fileexchange/121043-digraph-chord-chart)

Chen Lin
Last activity 2024-4-12

Spring is on the way!

What's the weather like in your place?

Toshiaki Takeuchi
Last activity 2024-4-24

If you use MatGPT, can you share how you use it?

MatGPT was launched on March 22, 2023 and I am amazed at how many times it has been downloaded since then - close to 16,000 downloads in one year. When AI Chat Playground came out on MATLAB Central, I thought surely that people will stop using MatGPT. Boy I was wrong.

In early 2023 I was playing with the new shiny toy called ChatGPT like everyone else but instead of having it tell me jokes or haiku, I wanted to know how I can use it on MATLAB, and I started collecting the prompts that worked. Someone suggested I should turn that into an app, and MatGPT was born with help from other colleagues.

Here is the question - what should I do with it now? Some people suggested I could add other LLMs like Gemini or Claude, but I am more interested in learning how people actually use it.

If you are a MatGPT user, do you mind sharing how you use the app?

http://www-pord.ucsd.edu/matlab/

David
Last activity 2024-4-2

Ghost page

I feel like no one at UC San Diego knows this page, let alone this server, is still live. For the younger generation, this is what the whole internet used to look like :)

ghost pages

David
Last activity 2024-4-1

Prompts Matter

I was in a meeting the other day and a coworker shared a smiley face they created using the AI Chat Playground. The image looked something like this:

And I suspect the prompt they used was something like this:

"Create a smiley face"

I imagine this output wasn't what my coworker had expected so he was left thinking that this was as good as it gets without manually editing the code, and that the AI Chat Playground couldn't do any better.

I thought I could get a better result using the Playground so I tried a more detailed prompt using a multi-step technique like this:

"Follow these instructions:

- Create code that plots a circle

- Create two smaller circles as eyes within the first circle

- Create an arc that looks like a smile in the lower part of the first circle"

The output of this prompt was better in my opinion.

These queries/prompts are examples of 'zero-shot' prompts, the expectation being a good result with just one query. As opposed to a back-and-forth chat session working towards a desired outcome.

I wonder how many attempts everyone tries before they decide they can't anything more from the AI/LLM. There are times I'll send dozens of chat queries if I feel like I'm getting close to my goal, while other times I'll try just one or two. One thing I always find useful is seeing how others interact with AI models, which is what inspired me to share this.

Does anyone have examples of techniques that work well? I find multi-step instructions often produces good results.

Athanasios Paraskevopoulos
Last activity 2024-3-31

Analysis and Visualization of Line Integral and Green's Theorem on a Square Path

The line integral

, where C is the boundary of the square

oriented counterclockwise, can be evaluated in two ways:

Using the definition of the line integral:

% Initialize the integral sum
integral_sum = 0;
% Segment C1: x = -1, y goes from -1 to 1
y = linspace(-1, 1);
x = -1 * ones(size(y));
dy = diff(y);
integral_sum = integral_sum + sum(-x(1:end-1) .* dy);
% Segment C2: y = 1, x goes from -1 to 1
x = linspace(-1, 1);
y = ones(size(x));
dx = diff(x);
integral_sum = integral_sum + sum(y(1:end-1).^2 .* dx);
% Segment C3: x = 1, y goes from 1 to -1
y = linspace(1, -1);
x = ones(size(y));
dy = diff(y);
integral_sum = integral_sum + sum(-x(1:end-1) .* dy);
% Segment C4: y = -1, x goes from 1 to -1
x = linspace(1, -1);
y = -1 * ones(size(x));
dx = diff(x);
integral_sum = integral_sum + sum(y(1:end-1).^2 .* dx);
disp(['Direct Method Integral: ', num2str(integral_sum)]);

Plotting the square path

% Define the square's vertices
vertices = [-1 -1; -1 1; 1 1; 1 -1; -1 -1];
% Plot the square
figure;
plot(vertices(:,1), vertices(:,2), '-o');
title('Square Path for Line Integral');
xlabel('x');
ylabel('y');
grid on;
axis equal;
% Add arrows to indicate the path direction (counterclockwise)
hold on;
for i = 1:size(vertices,1)-1
    % Calculate direction
    dx = vertices(i+1,1) - vertices(i,1);
    dy = vertices(i+1,2) - vertices(i,2);
    % Reduce the length of the arrow for better visibility
    scale = 0.2;
    dx = scale * dx;
    dy = scale * dy;
    % Calculate the start point of the arrow
    startx = vertices(i,1) + (1 - scale) * dx;
    starty = vertices(i,2) + (1 - scale) * dy;
    % Plot the arrow
    quiver(startx, starty, dx, dy, 'MaxHeadSize', 0.5, 'Color', 'r', 'AutoScale', 'off');
end
hold off;

Apply Green's Theorem for the line integral

% Define the partial derivatives of P and Q
f = @(x, y) -1 - 2*y;  % derivative of -x with respect to x is -1, and derivative of y^2 with respect to y is 2y
% Compute the double integral over the square [-1,1]x[-1,1]
integral_value = integral2(f, -1, 1, 1, -1);
disp(['Green''s Theorem Integral: ', num2str(integral_value)]);

Plotting the vector field related to Green’s theorem

% Define the grid for the vector field
[x, y] = meshgrid(linspace(-2, 2, 20), linspace(-2 ,2, 20));
% Define the vector field components
P = y.^2;  % y^2 component
Q = -x;    % -x component
% Plot the vector field
figure;
quiver(x, y, P, Q, 'b');
hold on;  % Hold on to plot the square on the same figure
% Define the square's vertices
vertices = [-1 -1; -1 1; 1 1; 1 -1; -1 -1];
% Plot the square path
plot(vertices(:,1), vertices(:,2), '-o', 'Color', 'k');  % 'k' for black color
title('Vector Field (P = y^2, Q = -x) with Square Path');
xlabel('x');
ylabel('y');
axis equal;
% Add arrows to indicate the path direction (counterclockwise)
for i = 1:size(vertices,1)-1
    % Calculate direction
    dx = vertices(i+1,1) - vertices(i,1);
    dy = vertices(i+1,2) - vertices(i,2);
    % Reduce the length of the arrow for better visibility
    scale = 0.2;
    dx = scale * dx;
    dy = scale * dy;
    % Calculate the start point of the arrow
    startx = vertices(i,1) + (1 - scale) * dx;
    starty = vertices(i,2) + (1 - scale) * dy;
    % Plot the arrow
    quiver(startx, starty, dx, dy, 'MaxHeadSize', 0.5, 'Color', 'r', 'AutoScale', 'off');
end
hold off;

Athanasios Paraskevopoulos
Last activity 2024-3-29

Computing a Surface Integral on a Sphere Using MATLAB

To solve a surface integral for example the

over the sphere

easily in MATLAB, you can leverage the symbolic toolbox for a direct and clear solution. Here is a tip to simplify the process:

Use Symbolic Variables and Functions: Define your variables symbolically, including the parameters of your spherical coordinates θ and ϕ and the radius r . This allows MATLAB to handle the expressions symbolically, making it easier to manipulate and integrate them.
Express in Spherical Coordinates Directly: Since you already know the sphere's equation and the relationship in spherical coordinates, define x, y, and z in terms of r , θ and ϕ directly.
Perform Symbolic Integration: Use MATLAB's `int` function to integrate symbolically. Since the sphere and the function are symmetric, you can exploit these symmetries to simplify the calculation.

Here’s how you can apply this tip in MATLAB code:

% Include the symbolic math toolbox
syms theta phi
% Define the limits for theta and phi
theta_limits = [0, pi];
phi_limits = [0, 2*pi];
% Define the integrand function symbolically
integrand = 16 * sin(theta)^3 * cos(phi)^2;
% Perform the symbolic integral for the surface integral
surface_integral = int(int(integrand, theta, theta_limits(1), theta_limits(2)), phi, phi_limits(1), phi_limits(2));
% Display the result of the surface integral symbolically
disp(['The surface integral of x^2 over the sphere is ', char(surface_integral)]);
% Number of points for plotting
num_points = 100;
% Define theta and phi for the sphere's surface
[theta_mesh, phi_mesh] = meshgrid(linspace(double(theta_limits(1)), double(theta_limits(2)), num_points), ...
                                  linspace(double(phi_limits(1)), double(phi_limits(2)), num_points));
% Spherical to Cartesian conversion for plotting
r = 2; % radius of the sphere
x = r * sin(theta_mesh) .* cos(phi_mesh);
y = r * sin(theta_mesh) .* sin(phi_mesh);
z = r * cos(theta_mesh);
% Plot the sphere
figure;
surf(x, y, z, 'FaceColor', 'interp', 'EdgeColor', 'none');
colormap('jet'); % Color scheme
shading interp; % Smooth shading
camlight headlight; % Add headlight-type lighting
lighting gouraud; % Use Gouraud shading for smooth color transitions
title('Sphere: x^2 + y^2 + z^2 = 4');
xlabel('x-axis');
ylabel('y-axis');
zlabel('z-axis');
colorbar; % Add color bar to indicate height values
axis square; % Maintain aspect ratio to be square
view([-30, 20]); % Set a nice viewing angle

Hans Scharler
Last activity 2024-4-19

Starter MATLAB Script

I am often talking to new MATLAB users. I have put together one script. If you know how this script works, why, and what each line means, you will be well on your way on your MATLAB learning journey.

% Clear existing variables and close figures
clear;
close all;
% Print to the Command Window
disp('Hello, welcome to MATLAB!');
% Create a simple vector and matrix
vector = [1, 2, 3, 4, 5];
matrix = [1, 2, 3; 4, 5, 6; 7, 8, 9];
% Display the created vector and matrix
disp('Created vector:');
disp(vector);
disp('Created matrix:');
disp(matrix);
% Perform element-wise multiplication
result = vector .* 2;
% Display the result of the operation
disp('Result of element-wise multiplication of the vector by 2:');
disp(result);
% Create plot
x = 0:0.1:2*pi; % Generate values from 0 to 2*pi
y = sin(x); % Calculate the sine of these values
% Plotting
figure; % Create a new figure window
plot(x, y); % Plot x vs. y
title('Simple Plot of sin(x)'); % Give the plot a title
xlabel('x'); % Label the x-axis
ylabel('sin(x)'); % Label the y-axis
grid on; % Turn on the grid
disp('This is the end of the script. Explore MATLAB further to learn more!');

basics