Fill area between different curves

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mikymike89 2018-3-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/386987-fill-area-between-different-curves

评论： Star Strider 2018-3-13

I cannot find a command to fill the area between the maximum and minimum values of these curves:

     x1 = [0 1 2.2 4];
     y1 = [0.5 2 1.8 1];
     x2 = [0 1.2 2 4];
     y2 = [0 1 2 1.5];
     x3 = [0 1 3 3.5];
     y3 = [0 1 2 1.5];
     figure
     plot(x1,y1);
     hold on   
     plot(x2,y2);
     hold on   
     plot(x3,y3);

I attached an image for better understand my request. Unfortunately, I found a solution just if Y is depending of X (e.g. : https://www.mathworks.com/matlabcentral/answers/180829-shade-area-between-graphs)

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Star Strider 2018-3-8

So your problem is now solved?

mikymike89 2018-3-8

no. My case is different from the e.g. found. I have "y" not depending of "x"

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Answer 1

Star Strider 2018-3-8

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/386987-fill-area-between-different-curves#answer_308941

在 MATLAB Online 中打开

It’s necessary to create common (x,y) values for all the curves with interpolation. Then the solution is straightforward.

If I understand correctly what you want, this works:

x1 = [0 1 2.2 4];
y1 = [0.5 2 1.8 1];
x2 = [0 1.2 2 4];
y2 = [0 1 2 1.5];
x3 = [0 1 3 3.5];
y3 = [0 1 2 1.5];
xm = [x1; x2; x3];                                                                  % Create ‘X’ Matrix
xl = [min(xm(:))  max(xm(:))];
xu = linspace(xl(1), xl(2), 1000);                                                  % Create Sorted Interpolation Vector
ym = [y1; y2; y3];                                                                  % Create ‘Y’ Matrix
for k1 = 1:size(xm,1)
    yi(k1,:) = interp1(xm(k1,:), ym(k1,:), xu, 'linear','extrap');                  % Interpolate To Provide Common (x,y) Values
end
ymin = min(yi);
ymax = max(yi);
figure
patch([xu(:)' fliplr(xu(:)')], [ymin fliplr(ymax)], [0.1 0.9 0.1], 'FaceAlpha',0.3) % Plot Filled Background
hold on
plot(x1,y1)
plot(x2,y2)
plot(x3,y3)

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Star Strider 2018-3-9

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Your actual data are column vector, not row vectors. (They are row vectors in your original post.) That required some changes in your code, and since in the interpolation, the independent ‘x’ variables must contain no duplicate values, required a call to the unique function to create them as such. Also, the third group is 1 element longer than the others, so I eliminated the values at x3(1), since that is 0 and none of the other ‘x’ vectors begins at 0.

With those changes, this works:

x1=HIST(:,1)';
y1=HIST(:,2)';
x2=HIST(:,3)';
y2=HIST(:,4)';
x3=HIST(:,5)';
y3=HIST(:,6)';
[x1u,ia1] = unique(x1);                                                             % Eliminate Duplicates, Return Unique Values & Indices
[x2u,ia2] = unique(x2);
[x3u,ia3] = unique(x3);
xm = [x1u; x2u; x3u(2:end)];                                                        % Create ‘X’ Matrix
xl = [min(xm(:))  max(xm(:))];
xu = linspace(xl(1), xl(2), 1000);                                                  % Create Sorted Interpolation Vector
ym = [y1(ia1); y2(ia2); y3(ia3(2:end))];                                            % Create ‘Y’ Matrix
for k1 = 1:size(xm,1)
    yi(k1,:) = interp1(xm(k1,:), ym(k1,:), xu, 'linear','extrap');                  % Interpolate To Provide Common (x,y) Values
end
ymin = min(yi);
ymax = max(yi);
figure
patch([xu(:)' fliplr(xu(:)')], [ymin fliplr(ymax)], [0.1 0.9 0.1], 'FaceAlpha',0.3) % Plot Filled Background
hold on
plot(x1,y1)
plot(x2,y2)

producing:

mikymike89 2018-3-13

So, isn't there a specific command to trim data on a certain line (for which I am sure that all data has the same length)? This is because I've more than thousands of data and I would like to avoid checking them manually. Moreover, I'm asking you this because I don't need all the data and I could use less; if there is a difference of vector length is maximum of ten line.

Star Strider 2018-3-13

在 MATLAB Online 中打开

There’s no one specific command. You would first need to use the size function to determine the vector sizes. Then compare the row size (dimension 1, so size(data,1) if ‘data’ is your array name), then compare them.

One way to do the initial check is:

sz1 = 200;                          % Row Size Of First Data Set
sz2 = 201;                          % Row Size Of Second Data Set
sz3 = 211;                          % Row Size Of Third Data Set
sz_eq = isequal(sz1, sz2, sz3);     % If All Are Equal=1, Not Equal = 0
min_rows = min([sz1 sz2 sz3]);      % Minimum Row Size
max_rows = max([sz1 sz2 sz3]);      % Maximum Row Size

You can of course define other criteria. Then trim your data matrices as you wish, the only constraint being that the ‘trimmed’ row size is less than ‘min_rows’.

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