Round towards specific values in an array

Hi, when I have 2 vectors, one vector has a larger length than the other. But they both have values that are approximately the same. Now I want to round and locate each element of the large vector in the short vector. So, for example:

A = [2000 1999 1998 1996 1993 .... 0] (dim=1 x a)

B = [2000 1995 1990 1985 1980 .... 0] (dim=1 x b)

I would now like to see that for example {2000 1999 1998} of A are rounded to {2000} in B and {1996 1993} in A to {1995} in B so that I can find the index of an element in B that corresponds to one (or more) rounded values in A.

I can imagine that you can do this with some kind of for-loop, but preferably I do not use that since it will become a nested loop and will cost a lot of computation time.

THanks a lot

Answer 1

[Tom Gaudette]

    % This solutions currently does it with loops just to get a picture of the problem.
    A = [2000 1999 1998 1996 1993 1990];
    B = [2000 1995 1990 1985 1980]; 
    for idx1=1:length(A);
      for idx2=1:length(B); 
          C(idx2,idx1)=A(idx1)-B(idx2);
      end;
    end
    % Now find the index of the min values
    [v,i]=min(abs(C));
    % 'i' now contants the list of locations in B that corespond to the nearest  
    % A value
    B(i)

[Adnane Youcef]

it works thnx

Answer 2

[Teja Muppirala]

This is one possible solution. If your vectors are very long though, this might be inefficient because it temporarily makes a big matrix to calculate all the differences.

A = -5 + 35*rand(1,100);
B = 0:5:25;  

[~,I] = min(abs(bsxfun(@minus,A,B')));

Anew = B(I);

[A; Anew]

Answer 3

[Tom R]

http://www.mathworks.com/matlabcentral/fileexchange/37674-roundtowardvec-m

Check this function out.

Answer 4

[Steven Lord]

A = [2000 1999 1998 1996 1993].';
B = [2000 1995 1990 1985 1980].';

Assuming all the elements of B are unique, interpolate to 'nearest'.

C = interp1(B, B, A, 'nearest');
result = table(A, C, 'VariableNames', ["Original data", "Rounded data"])

result = 5×2 table
    Original data    Rounded data
    _____________    ____________

        2000             2000    
        1999             2000    
        1998             2000    
        1996             1995    
        1993             1995