CODEWITHSUNDEEP
matlabmatrix
Chris
Chris

Reputation: 167

remove cells that satisfy a specific condition

I have a cell array which each cell is an n-by-n matrix. I want to delete the cells for which inv(cell{i}'*cell{i}) gives warning that matrix is close to singular. Thank you

Upvotes: 4

Views: 1974

Answers (3)

slayton
slayton

Reputation: 20319

Assuming you have already defined a issingular function defined you can use cellfun to get the indices of the cells that contain the matrices you want to remove.

c; % cell arry

singularIdx = cellfun((@x) issingular( inv(x' * x)), c);  %' added single quote for SO syntax

cFiltered = c(~singluarIdx);

You'll probably need to write your own function to check for singularity, for more information on that see this question: Fast method to check if a Matrix is singular? (non-invertible, det = 0)

Upvotes: 0

Sameh K. Mohamed
Sameh K. Mohamed

Reputation: 2333

Create a function that check for your condition:

function state = CheckElement(element)

if ([condition])
   state = 1;
else
   state = 0;
end

end

then do cellfun on all you cell array elements like the following:

indices = cellfun(@CheckElement,myCellArray);
cellArray(indices ) = [];

Upvotes: 1

Eitan T
Eitan T

Reputation: 32930

In general, removing elements is the easy part. If C is your array, removing cells specified by the indices in vector idx can be done by:

C(idx) = {};

Regarding your specific problem, to check if a matrix is "almost" singular or not can be done with rcond (if the result is close to zero, it's probably singular). To apply it to all cells you can use cellfun in the following way:

idx = cellfun(@(x)(rcond(x' * x) < 1e-12), C);

Adjust the threshold value to your liking. The resulting idx is a logical array with 1s at the location of singular matrices. Use idx to remove these elements from C as shown above.

Upvotes: 3

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