CODEWITHSUNDEEP
matlabcell-array
Stoka
Stoka

Reputation: 39

How to perform logical indexing of cell array for sparse matrix in coordinate format?

Let A be a sparse matrix in coordinate format [row(int) col(int) val(float)]. If a upper triangular sparse matrix of A is needed, then the same can be obtained using logical indexing like:

A = A(A(:,1) <= A(:,2), :);

If A is cell array [{row(int)} {col(int)} {val(string)}], how do I perform the same logical indexing as above in this case?

Upvotes: 0

Views: 835

Answers (3)

nispio
nispio

Reputation: 1744

How about this:

A = A(cellfun(@(x,y) x>=y, A(:,1),A(:,2)),:);

That should only keep the rows in which the value in the first column is greater than or equal to the value in the second column. You can change the x>=y comparison to anything you want, including string comparisons, etc.

Upvotes: 1

Oli
Oli

Reputation: 16035

You can use cell2mat to transform a column of the cell into a matrix that can be used as an index list:

A={1,2,'top';2,1,'bottom'}
A = 
    [1]    [2]    'top'   
    [2]    [1]    'bottom'
>> A(cell2mat(A(:,1))<=cell2mat(A(:,2)),:)
ans = 
    [1]    [2]    'top'

Upvotes: 2

Oli
Oli

Reputation: 16035

Why not using matlab built-in sparse matrix format?

Create a sparse matrix:

>> A=sparse([1 2],[2 1],1,2,2)
A =
   (2,1)        1
   (1,2)        1

Extract upper triangular part:

>> triu(A)
ans =
   (1,2)        1

Upvotes: 0

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