# Subtracting values in a matrix

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Jakub Nosek on 6 Nov 2017
Commented: Jakub Nosek on 6 Nov 2017
Hi, can I just ask you why the code below does not work? I am trying to subtract each value in a row from each other and if the condition is met then add 1 to matrix11(i,j). Apparently there's a problem with matrix10(i,:) expression.
matrix10=[1 7 20; 4 5 6; 7 8 9; 2 5 8];
[zk1, zk2] = size(matrix10);
matrix11=zeros(zk1,zk2);
for i=1:zk1
for j=1:zk2
if (abs(matrix10(i,j) - matrix10(i,:)) >= 2)
matrix11(i,j)=matrix11(i,j)+1;
end
end
end
matrix11 =
0 0 0
0 0 0
0 0 0
0 0 0

The problem is with this expression in the if statement:
if abs(matrix10(i,j) - matrix10(i,:)) >= 2
The left hand side is a vector but right side is a scalar -- which means that the condition is only met if all 3 differences exceed 2. What is the actual condition you want to check? If it is whether the total sum of differences exceeds 2, then you need to change the statement to:
if sum(abs(matrix10(i,j) - matrix10(i,:))) >= 2
Or it could be something else depending on what your condition actually is.
Jakub Nosek on 6 Nov 2017
Great! Thanks a lot!!