搜索讨论

cui,xingxing
上次活动时间: 2024-9-28

(Enhancement Request)"vision.VideoPlayer/VideoViewer" should be presented as a more modern player

In the past two years, MATHWORKS has updated the image viewer and audio viewer, giving them a more modern interface with features like play, pause, fast forward, and some interactive tools that are more commonly found in typical third-party players. However, the video player has not seen any updates. For instance, the Video Viewer or vision.VideoPlayer could benefit from a more modern player interface. Perhaps I haven't found a suitable built-in player yet. It would be great if there were support for custom image processing and audio processing algorithms that could be played in a more modern interface in real time.

Additionally, I found it quite challenging to develop a modern video player from scratch in App Designer.（If there's a video component for that that would be great）

-----------------------------------------------------------------------------------------------------------------

BTW，the following picture shows the built-in function uihtml function showing a more modern playback interface with controls for play, pause and so on. But can not add real-time image processing algorithms within it.

goc3
上次活动时间: 2024-12-3，13:54

Congratulations to William!

I was browsing the MathWorks website and decided to check the Cody leaderboard. To my surprise, William has now solved 5,000 problems. At the moment, there are 5,227 problems on Cody, so William has solved over 95%. The next competitor is over 500 problems behind. His score is also clearly the highest, approaching 60,000.

Please take a moment to congratulate @William.

J.K043006
上次活动时间: 2024-8-29

"corr" malfunctioning in cody

I've been working on some matrix problems recently(Problem 55225)

and this is my code

It turns out that "Undefined function 'corr' for input arguments of type 'double'." However, should't the input argument of "corr" be column vectors with single/double values? What's even going on there?

Chris Hooper
上次活动时间: 2024-8-29

uniqueN function would be useful

isequaln exists to return true when NaN==NaN.

unique treats NaN==NaN as false (as it should) requiring NaN to be replaced if NaN is not considered unique in a particular application. In my application, I am checking uniqueness of table rows using [table_unique,index_unique]=unique(table,"rows","sorted") and would prefer to keep NaN as NaN or missing in table_unique without the overhead of replacing it with a dummy value then replacing it again. Dummy values also have the risk of matching existing values in the table, requiring first finding a dummy value that is not in the table.

uniquen (similar to isequaln) would be more eloquent.

Please point out if I am missing something!

David
上次活动时间: 2024-8-8

Visual PDE

A library of runnable PDEs. See the equations! Modify the parameters! Visualize the resulting system in your browser! Convenient, fast, and instructive.

Visit https://visualpde.com/explore.html

Athanasios Paraskevopoulos
上次活动时间: 2024-12-10，6:40

Looking for Beginner Courses on Drone Programming

Hi everyone,

I've recently joined a forest protection team in Greece, where we use drones for various tasks. This has sparked my interest in drone programming, and I'd like to learn more about it. Can anyone recommend any beginner-friendly courses or programs that teach drone programming?

I'm particularly interested in courses that focus on practical applications and might align with the work we do in forest protection. Any suggestions or guidance would be greatly appreciated!

Thank you!

Muhammad
上次活动时间: 2024-8-26

What do you like most about MATLAB?

"What are your favorite features or functionalities in MATLAB, and how have they positively impacted your projects or research? Any tips or tricks to share?

DH
上次活动时间: 2024-8-8

Can someone tell me what's wrong with this code? This is a problem from Cody. For example, when n=3, the output should be the matrix [1 2 2 3 3 3]

function ans = your_fcn_name(n)
n;
j=sum(1:n);
a=zeros(1,j);
 for i=1:n
   a(1,((sum(1:(i-1))+1)):(sum(1:(i-1))+i))=i.*ones(1,i);     
 end
 disp

Marisa
上次活动时间: 2024-8-26

Can't click Roll the Dice!

I am trying to earn my Intro to MATLAB badge in Cody, but I cannot click the Roll the Dice! problem. It simply is not letting me click it, therefore I cannot earn my badge. Does anyone know who I should contact or what to do?

Gregory Vernon
上次活动时间: 2024-7-13

More easily enable CAD-like view mode

Something that had bothered me ever since I became an FEA analyst (2012) was the apparent inability of the "camera" in Matlab's 3D plot to function like the "cameras" in CAD/CAE packages.

For instance, load the ForearmLink.stl model that ships with the PDE Toolbox in Matlab and ParaView and try rotating the model.

clear

close all

gm = importGeometry( "ForearmLink.stl" );

pdegplot(gm)

To provide talking points, here's a YouTube video I recorded.

Things to observe:

Note that I cant seem to rotate continuously around the x-axis. It appears to only support rotations from [0, 360] as opposed to [-inf, inf]. So, for example, if I'm looking in the Y+ direction and rotate around X so that I'm looking at the Z- direction, and then want to look in the Y- direction, I can't simply keep rotating around the X axis... instead have to rotate 180 degrees around the Z axis and then around the X axis. I'm not aware of any data visualization applications (e.g., ParaView, VisIt, EnSight) or CAD/CAE tools with such an interaction.
Note that at the 50 second mark, I set a view in ParaView: looking in the [X-, Y-, Z-] direction with Y+ up. Try as I might in Matlab, I'm unable to achieve that same view perspective.

Today I discovered that if one turns on the Camera Toolbar from the View menubar, then clicks the Orbit Camera icon, then the No Principal Axis icon:

That then it acts in the manner I've long desired. Oh, and also, for the interested, it is programmatically available: https://www.mathworks.com/help/matlab/ref/cameratoolbar.html

I might humbly propose this mode either be made more discoverable, similar to the little interaction widgets that pop up in figures:

Or maybe use the middle-mouse button to temporarily use this mode (a mouse setting in, e.g., Abaqus/CAE).

Honzik
上次活动时间: 2024-7-18

Matlab Custom Font

I've noticed is that the highly rated fonts for coding (e.g. Fira Code, Inconsolata, etc.) seem to overlook one issue that is key for coding in Matlab. While these fonts make 0 and O, as well as the 1 and l easily distinguishable, the brackets are not. Quite often the curly bracket looks similar to the curved bracket, which can lead to mistakes when coding or reviewing code.

So I was thinking: Could Mathworks put together a team to review good programming fonts, and come up with their own custom font designed specifically and optimized for Matlab syntax?

jmgoldba
上次活动时间: 2024-6-21

Add Tools->Basic Fitting->...Weighted least squares

An option for 10th degree polynomials but no weighted linear least squares. Seriously? Jesse

https://blogs.mathworks.com/community/2015/02/26/lets-code-make-a-cody-video/

Ned Gulley
上次活动时间: 2024-6-13

Make a video: "How I Solved It"

Twitch built an entire business around letting you watch over someone's shoulder while they play video games. I feel like we should be able to make at least a few videos where we get to watch over someone's shoulder while they solve Cody problems. I would pay good money for a front-row seat to watch some of my favorite solvers at work. Like, I want to know, did Alfonso Nieto-Castonon just sit down and bang out some of those answers, or did he have to think about it for a while? What was he thinking about while he solved it? What resources was he drawing on? There's nothing like watching a master craftsman at work.

I can imagine a whole category of Cody videos called "How I Solved It". I tried making one of these myself a while back, but as far as I could tell, nobody else made one.

Here's the direct link to the video: https://www.youtube.com/watch?v=hoSmO1XklAQ

I hereby challenge you to make a "How I Solved It" video and post it here. If you make one, I'll make another one.

Ned Gulley
上次活动时间: 2024-6-25

What's your opinion of the Ans Hack?

The Ans Hack is a dubious way to shave a few points off your solution score. Instead of a standard answer like this

function y = times_two(x)
  y = 2*x;
end

you would do this

function ans = times_two(x)
  2*x;
end

The ans variable is automatically created when there is no left-hand side to an evaluated expression. But it makes for an ugly function. I don't think anyone actually defends it as a good practice. The question I would ask is: is it so offensive that it should be specifically disallowed by the rules? Or is it just one of many little hacks that you see in Cody, inelegant but tolerable in the context of the surrounding game?

Incidentally, I wrote about the Ans Hack long ago on the Community Blog. Dealing with user-unfriendly code is also one of the reasons we created the Head-to-Head voting feature. Some techniques are good for your score, and some are good for your code readability. You get to decide with you care about.

goc3
上次活动时间: 2024-6-7

Trick: Easy Digit Manipulation

There are a host of problems on Cody that require manipulation of the digits of a number. Examples include summing the digits of a number, separating the number into its powers, and adding very large numbers together.

If you haven't come across this trick yet, you might want to write it down (or save it electronically):

digits = num2str(4207) - '0'

That code results in the following:

digits =
     4     2     0     7

Now, summing the digits of the number is easy:

sum(digits)
ans =
    13

Chen Lin
上次活动时间: 2024-10-1

Welcome to the Cody Discussion Channel! Please Read Before Posting

Hello and a warm welcome to everyone! We're excited to have you in the Cody Discussion Channel. To ensure the best possible experience for everyone, it's important to understand the types of content that are most suitable for this channel.

Content that belongs in the Cody Discussion Channel:

Tips & tricks: Discuss strategies for solving Cody problems that you've found effective.
Ideas or suggestions for improvement: Have thoughts on how to make Cody better? We'd love to hear them.
Issues: Encountering difficulties or bugs with Cody? Let us know so we can address them.
Requests for guidance: Stuck on a Cody problem? Ask for advice or hints, but make sure to show your efforts in attempting to solve the problem first.
General discussions: Anything else related to Cody that doesn't fit into the above categories.

Content that does not belong in the Cody Discussion Channel:

Comments on specific Cody problems: Examples include unclear problem descriptions or incorrect testing suites.
Comments on specific Cody solutions: For example, you find a solution creative or helpful.

Please direct such comments to the Comments section on the problem or solution page itself.

We hope the Cody discussion channel becomes a vibrant space for sharing expertise, learning new skills, and connecting with others.

lazymatlab
上次活动时间: 2024-5-18

Helped a high school student for a physics problem with this.

A high school student called for help with this physics problem:

Car A moves with constant velocity v.
Car B starts to move when Car A passes through the point P.
Car B undergoes...
uniform acc. motion from P to Q.
uniform velocity motion from Q to R.
uniform acc. motion from R to S.
Car A and B pass through the point R simultaneously.
Car A and B arrive at the point S simultaneously.

Q1. When car A passes the point Q, which is moving faster?

Q2. Solve the time duration for car B to move from P to Q using L and v.

Q3. Magnitude of acc. of car B from P to Q, and from R to S: which is bigger?

Well, it can be solved with a series of tedious equations. But... how about this?

Code below:

%% get images and prepare stuffs
figure(WindowStyle="docked"), 
ax1 = subplot(2,1,1);
hold on, box on
ax1.XTick = [];
ax1.YTick = [];
A = plot(0, 1, 'ro', MarkerSize=10, MarkerFaceColor='r');
B = plot(0, 0, 'bo', MarkerSize=10, MarkerFaceColor='b');
[carA, ~, alphaA] = imread('https://cdn.pixabay.com/photo/2013/07/12/11/58/car-145008_960_720.png');
[carB, ~, alphaB] = imread('https://cdn.pixabay.com/photo/2014/04/03/10/54/car-311712_960_720.png');
carA = imrotate(imresize(carA, 0.1), -90);
carB = imrotate(imresize(carB, 0.1), 180);
alphaA = imrotate(imresize(alphaA, 0.1), -90);
alphaB = imrotate(imresize(alphaB, 0.1), 180);
carA = imagesc(carA, AlphaData=alphaA, XData=[-0.1, 0.1], YData=[0.9, 1.1]);
carB = imagesc(carB, AlphaData=alphaB, XData=[-0.1, 0.1], YData=[-0.1, 0.1]);
txtA = text(0, 0.85, 'A', FontSize=12);
txtB = text(0, 0.17, 'B', FontSize=12);
yline(1, 'r--')
yline(0, 'b--')
xline(1, 'k--')
xline(2, 'k--')
text(1, -0.2, 'Q', FontSize=20, HorizontalAlignment='center')
text(2, -0.2, 'R', FontSize=20, HorizontalAlignment='center')
% legend('A', 'B') % this make the animation slow. why?
xlim([0, 3])
ylim([-.3, 1.3])
%% axes2: plots velocity graph
ax2 = subplot(2,1,2);
box on, hold on
xlabel('t'), ylabel('v')
vA = plot(0, 1, 'r.-');
vB = plot(0, 0, 'b.-');
xline(1, 'k--')
xline(2, 'k--')
xlim([0, 3])
ylim([-.3, 1.8])
p1 = patch([0, 0, 0, 0], [0, 1, 1, 0], [248, 209, 188]/255, ...
    EdgeColor = 'none', ...
    FaceAlpha = 0.3);
%% solution
v = 1; % car A moves with constant speed.
L = 1; % distances of P-Q, Q-R, R-S
% acc. of car B for three intervals
a(1) = 9*v^2/8/L;
a(2) = 0;
a(3) = -1;
t_BatQ = sqrt(2*L/a(1)); % time when car B arrives at Q
v_B2 = a(1) * t_BatQ; % speed of car B between Q-R
%% patches for velocity graph
p2 = patch([t_BatQ, t_BatQ, t_BatQ, t_BatQ], [1, 1, v_B2, v_B2], ...
    [248, 209, 188]/255, ...
    EdgeColor = 'none', ...
    FaceAlpha = 0.3);
p3 = patch([2, 2, 2, 2], [1, v_B2, v_B2, 1], [194, 234, 179]/255, ...
    EdgeColor = 'none', ...
    FaceAlpha = 0.3);
%% animation
tt = linspace(0, 3, 2000);
for t = tt
    A.XData = v * t;
    vA.XData = [vA.XData, t];
    vA.YData = [vA.YData, 1];
    if t < t_BatQ
        B.XData = 1/2 * a(1) * t^2;
        vB.XData = [vB.XData, t];
        vB.YData = [vB.YData, a(1) * t];
        p1.XData = [0, t, t, 0];
        p1.YData = [0, vB.YData(end), 1, 1];
    elseif t >= t_BatQ && t < 2
        B.XData = L + (t - t_BatQ) * v_B2;
        vB.XData = [vB.XData, t];
        vB.YData = [vB.YData, v_B2];
        p2.XData = [t_BatQ, t, t, t_BatQ];
        p2.YData = [1, 1, vB.YData(end), vB.YData(end)];
    else
        B.XData = 2*L + v_B2 * (t - 2) + 1/2 * a(3) * (t-2)^2;
        vB.XData = [vB.XData, t];
        vB.YData = [vB.YData, v_B2 + a(3) * (t - 2)];
        p3.XData = [2, t, t, 2];
        p3.YData = [1, 1, vB.YData(end), v_B2];
    end
    txtA.Position(1) = A.XData(end);
    txtB.Position(1) = B.XData(end);
    carA.XData = A.XData(end) + [-.1, .1];
    carB.XData = B.XData(end) + [-.1, .1];
    drawnow
end