Removing values of an array greater then threshold value

Hello,

I have an array of size 500x1 and I want to make the values lesser than threshold value to zero while copying the same values of array which are less than the threshold. can I know how to do this.

thanks.

[Walter Roberson]

Huh? You want as output two arrays, one with the numbers that were less than the threshold, and the other being the original except with those lower numbers set to 0?

Or you just want to replace the values lower than the threshold with 0?

[Gova ReDDy]

Just one to replace the values lower than the threshold with 0

Answer 1

[Walter Roberson]

newmatrix = max(oldmatrix, 0);

The above would replace all negative values with 0.

newmatrix = oldmatrix;
newmatrix(oldmatrix < threshold) = 0;

[Benjamin Lender]

Dear Mr. Roberson,

I am dealing with large matrices n x n with n > 100,000, sometimes n > 1,000,000. The matrix is a sparse matrix.

The calculation terminates with "Requested array exceeds maximum array size preference. Creation of arrays greater than this limit may take a long time and cause MATLAB to become unresponsive."

Is there a way of doing this calculation that is more efficient in terms of required memory (or whatever storage is the bottleneck)?

I have unsuccessfully tried

A.*(A>Threshold))

as suggested by https://de.mathworks.com/matlabcentral/answers/27314-how-to-remove-elements-in-a-matrix-less-than-a-threshold