Remove unwanted data above the line

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TAN SAK JIE 2021-5-27

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/841005-remove-unwanted-data-above-the-line

评论： Image Analyst 2021-5-28

As describe above, how can I remove all the unwanted data above the curve magenta line .

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KSSV 2021-5-27

You have coordinates for both the data? I mean the magenta curve and the blue lines?

TAN SAK JIE 2021-5-28

Hello Sir.. i have attach the data for the curve magenta line :D

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Answer 1

Image Analyst 2021-5-28

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/841005-remove-unwanted-data-above-the-line#answer_711010

Since I don't think you're simply wanting to delete points above the magenta curve, I don't think you can just simply do bTrim(bLine>mLine) = NaN;

I don't think that will handle the case where the magenta curve bends around and goes backwards. So I'd make the magenta curve into a closed polygon with the upper left and upper right corners of the graph (which you can get with xlim and ylim) and then use inpolygon() to set those inside the polygon to null.

But you didn't attach your points and you accepted that answer, so whatever - at least you're happy with what it does. If not, write back, attach your data, and I'll give you my code.

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TAN SAK JIE 2021-5-28

matlab123.mat

Yes Sir.. there might be a problem when the magenta curve bends around and goes backwards. It cannot remove the data at the curve there

Here I attach my data for the curve

and the link is shown what i facing the problem now

https://www.mathworks.com/matlabcentral/answers/841285-point-not-match-and-connect-with-the-nearest-point-to-line?s_tid=srchtitle

Thanks :)

Image Analyst 2021-5-28

在 MATLAB Online 中打开

matlab123.mat

I don't know what's what. This is what I get:

fileName = 'matlab123.mat';
s = load(fileName)
Topwall = s.Topwall;
for col = 1 : 3
	plot(Topwall(:, col), '.');
	hold on;
end
legend

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Answer 2

Allen 2021-5-27

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https://ww2.mathworks.cn/matlabcentral/answers/841005-remove-unwanted-data-above-the-line#answer_710775

在 MATLAB Online 中打开

This can be accomplished using conditional indexing and reassigning values to the blue-line data. The following example assumes that the data for both the blue and magenta datasets are the same size. If they are not then you can resize one or the other set first using interp1. I am also assume that you have your x-data, blue-line data, and magenta-line data assigned to variables x, bLine, and mLine, respectively.

bTrim = bLine; % Initialize new blue line data variable
bTrim(bLine>mLine) = NaN; % Finds indices where bLine is greater than mLine, then assigns NaN to those indices
figure % Original data figure
plot(x,bLine,x,mLine)
figure % Trimmed blue line data figure
plot(x,bTrim,x,mLine)