Combining two vectors into a new one

Hi,

I am working on a dynamic programming problem and I now have two equal-sized vectors, say vector A and B. I am trying to generate a new vector that starts with the first element of vector B, then finds the closest value in A and takes it's index value, then records the value corresponding to this index in B. I want to make a loop and cover all values in my vector B. Is there a way to code this? (Vector A and B won't have the exact same values unfortunately, so the code will need to find the closest element's index)

Thanks!

Answer 1

[Johan]

I don't know if there is a builtin function to do that but you can achieve using translation, logical condition and find:

A = randi(10,5,1);
B = randi(10,5,1);
 % compute difference of each element of B with each element of A
 abs(B'-A)

ans = 5×5

1 0 3 4 3 2 1 2 3 2 4 3 0 1 0 5 4 1 0 1 4 3 0 1 0

 % minimum difference value
 min(abs(B'-A))

ans = 1×5

1 0 0 0 0

 % Create a logical mask of the position of the minimum difference
 min_distance_mask = abs(B'-A) == min(abs(B'-A))

min_distance_mask = 5×5 logical array
   1   1   0   0   0
   0   0   0   0   0
   0   0   1   0   1
   0   0   0   1   0
   0   0   1   0   1

%use find to get the index and rescale the index using the width of the array
%Equal distance increase the size of C compared to A and B
 C = mod(find(min_distance_mask)-1,size(min_distance_mask,2))+1 

C = 7×1

1 1 3 5 4 3 5

[Irem Sara]

This is exactly what I was looking for- thank you so much!

Answer 2

[KSSV]

A = rand(3) ;
B = rand(2) ; 
idx = knnsearch(B(:),A(:))

Also have a look on ismember, ismembertol.