Fill area between two curves

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Shri Harsha Bharadwaj 2021-2-16

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/747372-fill-area-between-two-curves

评论： Star Strider 2021-5-14

采纳的回答： Star Strider

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Hello,

I am tring to fill the area between the two ellipses. I am importing the values from Excel to plot the figure. After that I would like to fill the two ellipses with two different colors. How do I do that?.

CODE:

clc
clear all
load Phase12.mat
x = Phase1.x;
y = Phase1.z;
plot(x,y);
fill(x,y,'g');
hold on
a = Phase1.a;
b = Phase1.b;
plot(a,b);
% fill(a,b,'q')

x,y,a and b are the names of the four columns that I have imported from excel. x,y represents the bigger ellipse. I tried using some of the patch codes, but it did not work out. Can someone please help me with this?

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Adam Danz 2021-4-2

Just FYI so you don't have to wait for your answers in the future, this topic has been addressed many times in the forum and there is a clear example in the patch documentation.

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Star Strider 2021-2-16

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Try something like this:

t = linspace(0, 2*pi);
x = ([1;2]*cos(t)).';                                                               % Produces (Nx2) Matrix
y = ([1;2]*sin(t)).';                                                               % Produces (Nx2) Matrix
figure
patch([x(:,2); flipud(x(:,1))], [y(:,2); flipud(y(:,1))], 'g', 'EdgeColor','none')  % Create ‘patch’ Object
hold on
plot(x(:,1), y(:,1), '-r')                                                          % Circle Outlines
plot(x(:,2), y(:,2), '-r')                                                          % Circle Outlines
hold off
axis('equal')

If your data are row vectors, do this:

patch([x fliplr(a)], [y fliplr(b)], 'g')

If they are column vectors:

patch([x; flipud(a)], [y; flipud(b)], 'g')

That should work.

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Star Strider 2021-2-17

编辑：Star Strider 2021-2-17

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My pleasure!

There are NaN values in some of your data. That was the problem.

This works:

T1 = readtable('3Phase1.csv', 'VariableNamingRule','preserve');
xz = [T1.x T1.z];                                                                       % Concatenate Vectors
xz = xz(~any(isnan(xz),2),:);                                                           % Remove ‘NaN’ Rows
ab = [T1.a T1.b];                                                                       % Concatenate Vectors
ab = ab(~any(isnan(ab),2),:);                                                           % Remove ‘NaN’ Rows
figure
patch([xz(:,1); flipud(ab(:,1))], [xz(:,2); flipud(ab(:,2))], 'g', 'EdgeColor','none')  % Create ‘patch’ Object
hold on
plot(xz(:,1), xz(:,2), '-b')                                                            % Curve Outlines
plot(ab(:,1), ab(:,2), '-b')                                                            % Curve Outlines
hold off
axis('equal')

producing:

It is easier to concatenate the vectors into their respective matrices in order to remove the NaN values.

Other than removing the NaN values and adapting my code to your variables, my original code is essentially unchanged.

Star Strider 2021-2-17

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My pleasure!

(I slightly edited my earlier Comment to make the code more robust.)

‘If I wanted to color the smaller ellipse in the center, would I have to do something similar to this?’

Yes, however it would be easier. To fill the inner curve, simply add this patch call:

patch(ab(:,1), ab(:,2), 'r')                                                            % Fill Inner Curve

so the slightly revised, complete code is now:

T1 = readtable('3Phase1.csv', 'VariableNamingRule','preserve');
xz = [T1.x T1.z];                                                                       % Concatenate Vectors
xz = xz(~any(isnan(xz),2),:);                                                           % Remove ‘NaN’ Rows
ab = [T1.a T1.b];                                                                       % Concatenate Vectors
ab = ab(~any(isnan(ab),2),:);                                                           % Remove ‘NaN’ Rows
figure
patch([xz(:,1); flipud(ab(:,1))], [xz(:,2); flipud(ab(:,2))], 'g', 'EdgeColor','none')  % Create ‘patch’ Object
hold on
plot(xz(:,1), xz(:,2), '-b')                                                            % Curve Outlines
plot(ab(:,1), ab(:,2), '-b')                                                            % Curve Outlines
patch(ab(:,1), ab(:,2), 'r')                                                            % Fill Inner Curve
hold off
axis('equal')

producing:

Of course, choose whatever line colours and inner-curve fill colour you want.

Star Strider 2021-5-13

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I wish it was simple! I have no idea how to plot them because I have no idea what the variables are.

The plot3 function would appear to be appropriate. Experriment with it to get the result you want.

My best effort —

C1 = readcell('https://www.mathworks.com/matlabcentral/answers/uploaded_files/617108/test1.csv');

T1 = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/617108/test1.csv', 'VariableNamingRule','preserve');

First10Rows = T1(1:10,:)

First10Rows = 10×7 table

Chart Count Velocity [ m s^-1 ] Z Var4 Chart Count_1 Velocity [ m s^-1 ]_1 Z_1 ___________ ___________________ _____ ____ _____________ _____________________ _____ 0 0 0.008 NaN 0 0.000377 0.006 1 0.00156 0.008 NaN 1 0.000678 0.006 2 0.00313 0.008 NaN 2 0.000979 0.006 3 0.00469 0.008 NaN 3 0.00128 0.006 4 0.00626 0.008 NaN 4 0.00158 0.006 5 0.00782 0.008 NaN 5 0.00188 0.006 6 0.00939 0.008 NaN 6 0.00218 0.006 7 0.011 0.008 NaN 7 0.00248 0.006 8 0.0125 0.008 NaN 8 0.00279 0.006 9 0.0141 0.008 NaN 9 0.00309 0.006

figure

plot3(T1{:,3},T1{:,5},T1{:,2})

hold on

plot3(T1{:,3},T1{:,5},T1{:,6})

hold off

grid on

The arguments to the plot3 call refer to the columns of ‘T1’, so ‘T1{:,1}’ is the first column, and so for the others.

I added the readcell call because readtable read in one of the variables as NaN and I wanted to see what that was. It turns out to apparently be a vector of empty cells.

Star Strider 2021-5-13

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As always, my pleasure!

They are plotted in the same location because I have no idea what the variables are, or how you would like them plotted. The ‘Velocity’ variables are obviously the dependent variables, however I have no idea what the independent variables should be. (The plot3 function requires two independent variables and one dependent variable.)

Perhaps —

T1 = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/617108/test1.csv', 'VariableNamingRule','preserve');

First10Rows = T1(1:10,:)

First10Rows = 10×7 table

figure

plot3(T1{:,1},T1{:,3},T1{:,2})

hold on

plot3(T1{:,5},T1{:,7},T1{:,6})

hold off

grid on

would work instead.

Shri Harsha Bharadwaj 2021-5-13

Thanks for the help sir. I was testing it out. Thanks a ton again.

Star Strider 2021-5-14

As always, my pleasure!

Apparently the data file changed (I have been away doing other things), since it is not the same one I initially plotted.

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