How can I fill in the area between two curves? The curves are not the same length and also don't form a closed shape.

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Srh Fwl 2022-4-8

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https://ww2.mathworks.cn/matlabcentral/answers/1692110-how-can-i-fill-in-the-area-between-two-curves-the-curves-are-not-the-same-length-and-also-don-t-for

评论： Voss 2022-4-8

采纳的回答： Voss

testFig.jpg

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The plot at the top is an example of what I have. There are two data series. The top series (filled squares) represents maximum values of my data. For each maximum value data point, there is usually (but not always) a minimum value data point vertically below.

I would like to do something like in the second figure, where I shade the area between the two curves--or better still, between each data pair (the maximum and minimum value at a particular x axis value) and plot one of the points in the pair as solid.

My problem is that I have been through previous questions here and can't get anything to work for my situation. In my example, there is a minimum value for each maximum value but that is not always the case and also, the two curves don't form a closed shape. The errors I'm getting seem to be related to these issues. Does anyone know if there's a straightforward way to do this? Thank you for any advice.

Here are the data. I left the "NaN" in because that's the nature of my data and I have to deal with them.

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Answer 1

Voss 2022-4-8

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在 MATLAB Online 中打开

x1 = [1.0000; 3.0000; 4.5000; 6.0000; 8.0000; 11.0000; 16.0000; 20.0000; 25.0000; 30.0000];

x2 = [16.0027; 24.1943; 27.7769; 34.8065; NaN; 56.2825; 68.2554; 73.0484; 76.4253; NaN];

y2 = [14.0410; NaN; 25.0441; 30.4932; 36.3988; 50.6604; 61.9821; 71.4331; 73.9582; NaN];

% 44.5189 replaced by NaN in x2 for demonstration

% 20.9402 replaced by NaN in y2 for demonstration

good_x2 = find(~isnan(x2));

good_y2 = find(~isnan(y2));

patch( ...

x1([good_x2; good_y2(end:-1:1)]), ...

[x2(good_x2); y2(good_y2(end:-1:1))], ...

'r','EdgeColor','none','FaceAlpha',0.5)

hold on

plot(x1,x2,'rs','MarkerFaceColor','r')

plot(x1,y2,'rs')

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Voss 2022-4-8

在 MATLAB Online 中打开

To make the edges smoother, you'd have to introduce additional data points, e.g., by interpolating between the given data using some non-linear method (because using linear interpolation will give you the same straight-line segments you already have)

x1 = [1.0000; 3.0000; 4.5000; 6.0000; 8.0000; 11.0000; 16.0000; 20.0000; 25.0000; 30.0000];

x2 = [16.0027; 24.1943; 27.7769; 34.8065; NaN; 56.2825; 68.2554; 73.0484; 76.4253; NaN];

y2 = [14.0410; NaN; 25.0441; 30.4932; 36.3988; 50.6604; 61.9821; 71.4331; 73.9582; NaN];

% 44.5189 replaced by NaN in x2 for demonstration

% 20.9402 replaced by NaN in y2 for demonstration

% only interpolate with non-NaN values:

good_x2 = find(~isnan(x2));

good_y2 = find(~isnan(y2));

% interpolate to 100 points

x1_patch = linspace(min(x1),max(x1),100).';

x2_patch = interp1(x1(good_x2),x2(good_x2),x1_patch,'makima',NaN);

y2_patch = interp1(x1(good_y2),y2(good_y2),x1_patch,'makima',NaN);

% make the patch the same way as before, but now use the interpolated

% points:

good_x2 = find(~isnan(x2_patch));

good_y2 = find(~isnan(y2_patch));

patch( ...

x1_patch([good_x2; good_y2(end:-1:1)]), ...

[x2_patch(good_x2); y2_patch(good_y2(end:-1:1))], ...

'r','EdgeColor','none','FaceAlpha',0.5)

hold on

plot(x1,x2,'rs','MarkerFaceColor','r')

plot(x1,y2,'rs')

Srh Fwl 2022-4-8

Thank you, that's very kind. Really appreciate your help.

Voss 2022-4-8

You're welcome!

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How can I fill in the area between two curves? The curves are not the same length and also don't form a closed shape.

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How can I fill in the area between two curves? The curves are not the same length and also don't form a closed shape.

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