# How can I do setdiff() between 2 arrays row by row without a loop?

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Izan Segarra on 21 Feb 2019
Commented: Izan Segarra on 21 Feb 2019
I'm trying to do the difference between 2 arrays with setdiff function but I don't get the expected result.
A = [15 8 5 9 10 14 17 7 20 12 6 16 2 4 11 13 3 1 19 18
10 19 13 15 1 16 6 14 17 8 11 18 20 5 2 12 7 9 4 3
15 8 5 9 10 14 17 7 20 12 6 16 2 4 11 13 3 1 19 18
13 12 3 14 4 19 2 16 10 18 20 6 15 5 7 17 1 9 11 8
13 12 3 14 4 19 2 16 10 18 20 6 15 5 7 17 1 9 11 8];
B = [16 19 15 5 8 1 3 20 14 18
4 14 13 2 20 9 15 7 6 12
14 2 12 13 4 8 5 19 18 20
3 10 19 13 15 1 16 6 14 17
12 11 6 10 13 7 16 19 15 5];
When I execute the instruction I get:
setdiff(A,B)
ans =
0×1 empty double column vector
But I would like to get:
out =[ 9 10 17 7 12 6 2 4 11 13
10 19 1 16 17 8 11 18 5 3
15 9 10 17 7 6 16 11 3 1
12 4 2 18 20 5 7 9 11 8
3 14 4 2 18 20 17 1 9 8];
Is there some way to get it without a loop?

Fangjun Jiang on 21 Feb 2019
While your result shows that out is a 5x10 array, it is not guaranted in a generic case, because if you do setdiff() row by row on A and B, the number of elements will not always be the same row by row.
Why so obsessed with "no for-loop"? For-loop could be simple, faster and easy to understand. I can think of one way to do your task without for-loop, but do you think it is easy to follow?
ca=mat2cell(A,repmat(1,1,size(A,1)),size(A,2))
cb=mat2cell(B,repmat(1,1,size(B,1)),size(B,2))
out=cell2mat(cellfun(@(a,b) setdiff(a,b),ca,cb,'uniformoutput',false))
Izan Segarra on 21 Feb 2019
Thank you for your answer. I'm trying to learn how to execute actions in Matlab in different ways.

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