MATLAB: Replace values in one column based on the content in several other columns.

coordinatesreplace

Hi
I have two matrices containing x,y and z coordinates. These matrices also contain a column with values for each point.
Looks something like this:
A=[x y z value, 1 1 1 1; 1 2 1 0, 2 1 1 3, 2 1 2 4]
B=[x y z value, 1 1 1 1; 1 2 1 0]
the first matrix (A) have much more values than the second one (B). What i am trying to do is to replace the values in the large matrix (A) with the values from the smaller matrix (B) whenever the coordinates are the same. Thus the values in the x y and z column need to match.
Any ideas how to solve this?

Best Answer

A = [1 1 1 0; 
    1 2 1 1; 
    2 1 1 3;
    1 1 1 3;
    2 1 2 4] 
B = [1 1 1 1; 
     1 2 1 0]
 
[b,loc] = ismember(A(:,1:3),B(:,1:3),'rows');
A(b,:) = B(loc(b),:);
The result after replacement is
A =
     1     1     1     1
     1     2     1     0
     2     1     1     3
     1     1     1     1
     2     1     2     4
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