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plotting values greater than threshold
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shobhit mehrotra
on 12 Aug 2014
Commented: ishbish
on 19 Feb 2018
im trying to plot values greater than a threshold in a different color. for example i want to plot values greater than 100 in the image in red
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Accepted Answer
Image Analyst
on 12 Aug 2014
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/175381/image.jpeg)
% Create sample data.
y = randi(160, 1, 40); % Array of random numbers
x = 1 : length(y);
% Plot everything with blue spots and blue lines between them.
plot(x, y, 'bo-', 'LineWidth', 2, 'MarkerSize', 7);
grid on;
% Now define a threshold.
threshold = 100;
moreThanThreshold = y > 100; % Logical indexes.
% Extract those over the threshold into new arrays.
over_x = x(moreThanThreshold);
over_y = y(moreThanThreshold);
% Now plot those over 100 with red stars over the first set of points.
hold on; % Important so you don't blow the first plot away.
plot(over_x, over_y, 'r*', 'LineWidth', 2, 'MarkerSize', 13);
3 Comments
Image Analyst
on 12 Feb 2018
Start a new question and attach some actual data, and if possible a picture of what you'd like to see.
ishbish
on 19 Feb 2018
I ultimately decided to apply a rotation matrix to my data and then just do it as described above, much easier! Thank you for the advice though.
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