# Compare two matrices of different dimensions

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MRC on 29 Apr 2014
Commented: MRC on 29 Apr 2014
I have a matrix B of dimension bx2 and a matrix A of dimension ax5 with the following characteristics:
B=[3 1;
3 2;
3 3;
5 18] %In the first column of B elements are always in ascending order but can be repeated more than once
A=[1 18 19 19 20;
2 7 8 9 10;
3 1 2 2 3;
4 18 19 19 20;
5 18 19 19 20;
6 11 12 13 14] %In the first column of A elements are always in ascending order, they start from 1 and end at a=6 and they are at a distance of 1
I want to construct a matrix C of dimension ax5
C=[1 0 0 0 0;
2 0 0 0 0;
3 1 1 1 1;
4 0 0 0 0;
5 1 0 0 0;
6 0 0 0 0]
In C I do the following: I take A(i,1) and pick the rows j of A with B(j,1) equal to A(i,1); for these rows I pick B(j,2) and reports C(i,h)=1 is B(j,2)=A(i,h).
If B(:,1) started with 1 and ended with 6 a possible answer would be
x = accumarray(B(:,1),B(:,2),[max(B(:,1)),1],@(x){x});
C = [A(:,1),cell2mat(arrayfun(@(z)ismember(A(z,2:end),x{z}),A(:,1),'un',0))]
as suggested here
But in this case B(:,1) does not necessarily start with 1 and end with 6 even if it has for sure elements <=6 and >=1
MRC on 29 Apr 2014
Yes, thanks question edited.

the cyclist on 29 Apr 2014
B=[3 1;
3 2;
3 3;
5 18] %In the first column of B elements are always in ascending order but can be repeated more than once
A=[1 18 19 19 20;
2 7 8 9 10;
3 1 2 2 3;
4 18 19 19 20;
5 18 19 19 20;
6 11 12 13 14] %In the first column of A elements are always in ascending order, they start from 1 and end at a=6 and they are at a distance of 1
C = zeros(size(A));
C(:,1) = A(:,1);
for ii = 1:size(A,1)
C(ii,2:end) = ismember(A(ii,2:end),B(B(:,1)==ii,2:end))
end
MRC on 29 Apr 2014
Any idea without looping?