I'd like to use an example to show what I want.
A = [5 1 2 4 3]; % of distinct values
B = [3 3 1 5 2];
Can I find a library function implemented in MATLAB such that:
C = [5 5 2 3 1] = someFun(A, B)
i.e. C(i) = find(A == B(i))
Note that I am asking for a library function, as in that case it is highly optimized. If you are sure there doesn't exist such a function, that is also an answer.
I would do:
IX(A) = [1:length(A)];
C=IX(B)
This is 10 times faster than the ismember solution:
A=randperm(1e5);
B=ceil(rand(1,1e4)*length(A));
tic;
[D,C1]=ismember(B,A);
toc % Elapsed time is 0.013728 seconds.
tic
IX(A) = [1:length(A)];
C=IX(B);
toc % Elapsed time is 0.001506 seconds.
But this can be used under stricter conditions:
A contains only unique integers.B(i) < max(A) for all imax(A)
A couple of solutions:
C = zeros(size(B));
for i=1:numel(B)
C(i) = find(A == B(i));
end
C = arrayfun(@(n)find(A==n), B)
[C,~] = find( bsxfun(@eq, B, A.') )
[~,C] = ismember(B,A)
'. It won't work if A is complex. It should be .'
Can you clarify your question a little bit?
If you want a function that returns the index of A that contains the value B(i) then a function like this should work:
for(int i = 0; i < B.length; i++)
{
for(int q = 0; q < A.length; q++)
{
if(B[i] == A[q])
C[i] = q;
}
}
