# how to remove zeros from the matrix?

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Junseob Kim on 25 Nov 2019
Commented: Junseob Kim on 25 Nov 2019
Hello, I want to remove zero values from the matrix and cut the last elements of odd rows. For example, if I have a matrix
A=[1, 0, 2, 0, 3 ;
0, 4, 0, 5, 0 ;
6, 0, 7, 0, 8]
and, I want to make matrix like
B=[1, 2;
4, 5;
6, 7]

Junseob Kim on 25 Nov 2019
And yes. If I have n zeros in odd rows, there are n+1 zeros in even rows.
James Tursa on 25 Nov 2019
Is it always the checkerboard pattern shown?
Junseob Kim on 25 Nov 2019
Yes it is.

the cyclist on 25 Nov 2019
Edited: the cyclist on 25 Nov 2019
I think this does what you want:
% Replicate A into B
B = A;
% For the even-numbered rows, circularly shift the elements
B(2:2:end,:) = circshift(B(2:2:end,:),-1,2);
% Remove any columnn with a zero
B(:,any(B==0)) = [];

#### 1 Comment

Junseob Kim on 25 Nov 2019
Thank you so much!!

Guillaume on 25 Nov 2019
A=[1, 0, 2, 0, 3 ;
0, 4, 0, 5, 0 ;
6, 0, 7, 0, 8];
B = reshape(nonzeros(A(:, 1:end-1).'), [], size(A, 1)).'

#### 1 Comment

Junseob Kim on 25 Nov 2019
Thank you so much!!

Adam Danz on 25 Nov 2019
This approach extracts the first two non-zero elements per row. If there are no two non-zero elements in each row an error is thrown.
A=[
1, 0, 2, 0, 3 ;
0, 4, 0, 5, 0 ;
6, 0, 7, 0, 8];
B=[1, 2;
4, 5;
6, 7];
% Number of non-zeros per row or A
numNonZeros = sum(A~=0,2);
% Replace the non-zeros after the 2nd non-zero in
% each row with 0s
A(cumsum(A~=0,2) > 2) = 0;
% Confirm that we end up with 2 non-0s in each row
if (unique(sum(A~=0,2))>0) ~= true
error('Assumption violation: the number of non-zeros in each row of A is unexpected.')
end
A = A.';
B = reshape(A(A~=0),2,size(A,2)).';

#### 1 Comment

Junseob Kim on 25 Nov 2019
Thank you so much!!

Kaspar Bachmann on 25 Nov 2019
Edited: Kaspar Bachmann on 25 Nov 2019
A=[1, 0, 2, 0, 3 ; 0, 4, 0, 5, 0 ; 6, 0, 7, 0, 8]
Var = A;
Var(:,length(Var)) = [];
for i = 1:size(Var,1)
t = Var(i,:);
idx = find(t>0);
B(i,:) = t(idx);
end
Its a bit messy, but it should work.

#### 1 Comment

Junseob Kim on 25 Nov 2019
Thank you so much!!