Selecting close matches from one array based on another reference array

Question

I have an array A and a reference array B. Size of A is at least as big as B. e.g.

A = [2,100,300,793,130         


        

Answer 1

You can use MATLAB interp1 function that exactly does what you want.
option nearest is used to find nearest points and there is no need to specify a threshold.

out = interp1(A, A, B, 'nearest', 'extrap');

comparing with other method:

A = sort(randi([0,1000000],1,10000));

B = sort(randi([0,1000000],1,4000));

disp('---interp1----------------')
tic
    out = interp1(A, A, B, 'nearest', 'extrap');
toc
disp('---subtraction with threshold------')
%numpy version is the same
tic
    [dists, ind] = min(abs(bsxfun(@minus, A, B.')), [], 2);
toc

Result:

---interp1----------------
Elapsed time is 0.00778699 seconds.
---subtraction with threshold------
Elapsed time is 0.445485 seconds.

interp1 can be used for inputs larger than 10000 and 4000 but in subtrction method out of memory error occured.