Question

I have a matrix that is like the following:

a = [10 0; 12 5; 10 0; 12 0; 15 0; 15 2];
a =

10     0
12     5
10     0
12     0
15     0
15     2

I am looking to create a new matrix which find and replaces the zeros with a value that is dependent on the first column’s value. The key is this matrix:

Key =

10   100
12   200
15   300

If the value is already greater than zero in the first column I would like to leave it. The output would look like this:

Output =

10   100
12     5
10   100
12   200
15   300
15     2

Answer 1

You can do it in one line using logical indexing smartly:

a(~a(:,2),2)=arrayfun(@(x)Key(Key(:,1)==x,2),a(~a(:,2),1))

%a =    
%    10   100
%    12     5
%    10   100
%    12   200
%    15   300
%    15     2