# Comparing Elements of two matrices if loop

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Esther Roosenbrand on 20 Sep 2017
Commented: OCDER on 22 Sep 2017
Hi, I want to compare two matrices one with size m*n and the other 2*k. The second matrix (2*k) indicates values which need to be satisfied by the m*n matrix. Basically, I calculated a value in the second matrix for 360 degrees of a circle. In the first matrix measurements of these values for a circle. In the end I want to know how many times both values, the 360 degrees and the values are met.
Cedric Wannaz on 21 Sep 2017
Edited: Cedric Wannaz on 21 Sep 2017
By counting, do you mean checking if there was one match?
For a given day you have on row of B, which is a single pair of elevation and azimuth. Then for the same day in A you have 24 pairs. How is it possible that you get twice (or more) the same pair of values from A when pair are given hourly?

OCDER on 21 Sep 2017
Hi Esther, this is one of many ways to do this.
%Reshape A into 2-columns matrix (called Ar) to avoid having to use nested for loops later
Ar = reshape([A(:, 1:2:end) A(:, 2:2:end)], numel(A)/2, 2);
%R will store value = 1 if conditions are met, value = 0 if conditions fail
R = zeros(size(Ar, 1), 1);
for k = 1:size(Ar, 1)
%if azimuth and elevation in Ar is greater than ANY from B, change R(k) to 1
if any( Ar(k, 1) >= B(:, 1) & Ar(k, 2) >= B(:, 2))
R(k) = 1;
end
end
%Number of times conditions are met per hour (row) for all day (col)
R = reshape(R, size(A, 1), size(A, 2)/2);
R =
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
%Number of times conditions are met per day
Rday = sum(R, 1);
Rday =
0 0
%Number of times conditions are met per year
Ryear = sum(Rday);
Ryear =
0
##### 2 CommentsShowHide 1 older comment
OCDER on 22 Sep 2017
You're welcome!

Cedric Wannaz on 21 Sep 2017
Edited: Cedric Wannaz on 21 Sep 2017
Or you can operate in 3D:
A = [-10, 2, -8, 4; ...
-4, 6, -3, 7; ...
2, 5, 3, 6] ;
B = [ 3, 6; ...
-8, 4] ;
dayHasMatch = squeeze(any(all(reshape(A, size(A, 1), 2, []) - permute(B, [3,2,1]) == 0, 2)))
with that you get
dayHasMatch =
2×1 logical array
0
1
which indicates that there was a match on day 2.
PS: and if you have an old version of MATLAB, the expansion must be performed using BSXFUN, and you can use a test of equality directly instead of checking that the difference is null:
dayHasMatch = squeeze(any(all(bsxfun(@eq, reshape(A, size(A, 1), 2, []), permute(B, [3,2,1])), 2)))