# How do I get rid of certain values with the same X-axis value in a certain range?

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Michael Arvin on 23 Feb 2022
Edited: David Goodmanson on 23 Feb 2022
Hello. I am trying to ignore/delete certain points in my data/plot. The x-axis is the time and the y-axis is the value. The time and value are both in 2 different matrices. The size of each is 8192. If I zoom in, it looks like this. I am trying to get rid of the value at a certain time that are more than the median within a certain range (for example +/-10).
Any ideas on how to do it?
Thank you very much!

David Goodmanson on 23 Feb 2022
Edited: David Goodmanson on 23 Feb 2022
Hi Michael,
here is one way, assuming that x (many values of which are repeated) and y are two columns.
tol = 10;
a = polyfit(x,y,1);
y1 = polyval(a,x);
ind = abs(y1-y) > tol;
x(ind) = [];
y(ind) = [];
The data appears to be very linear, so the code fits a straight line and kills off the points that are too far away from the line. This is not quite the same as a) finding the mean value of y for each group with the same x and b) killing off the points that deviate too much from each mean, but the results must be really similar.

KSSV on 23 Feb 2022
Put a logical conditioning, get indices and remove those points. Simple.
Example:
y = rand(1,10) ; % random data for demo
idx = y > 0.5 ; % get indices of values greater than 0.5
y(idx)= []; % remove them from y