# count of non zero elements of a row vector in a loop

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Georgios Kirkinezos on 28 Oct 2020
Commented: Peter O on 28 Oct 2020
Hi everyone,
i want to count the nonzero elements of a row-vector in a loop, i have the initial (360,1000) matrix u_new
for i=1:360;
for j=1:1000;
if u_new(i,j)==0 %%% here i transformed zeros to Nan, to use the following command isnan
u_new(i,j)=NaN;
insample_u_new=isnan(u_new(i,:))==0; %%% in this row-vector the possible values are 0 or 1, i am interested in getting the number of ones
P = numel(insample_u_new(i,j)~= 0); %%%here is the problem
end
end
end
I want the output P to be the number of the nonzero elements (ones) from the row-vector u_new=u(:,1:1000) for the loop.

Peter O on 28 Oct 2020
Try the nnz function.
It sounds like you're trying to count the number of nonzero elements in each row? Use arrayfun to apply this function to each row of the matrix (extracting the row index).
NZ = arrayfun(@(ix) nnz(u_new(ix,:)),1:size(u_new,1))
NZ will be a 1 x n_rows vector containing the nonzero element counts for each row.
##### 2 CommentsShowHide 1 older comment
Peter O on 28 Oct 2020

KSSV on 28 Oct 2020