Remove unwanted data above the line

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TAN SAK JIE on 27 May 2021
Commented: Image Analyst on 28 May 2021
As describe above, how can I remove all the unwanted data above the curve magenta line .
TAN SAK JIE on 28 May 2021
Hello Sir.. i have attach the data for the curve magenta line :D

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Answers (2)

Image Analyst
Image Analyst on 28 May 2021
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.
Image Analyst
Image Analyst on 28 May 2021
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;

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Allen on 27 May 2021
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
figure % Trimmed blue line data figure
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TAN SAK JIE on 28 May 2021
Edited: Image Analyst on 28 May 2021
Sir, now I am facing another problem for that plot. Could you help me to solve it too?
Here is the link :

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