MATLAB: Replace a value if a condition is met

conditionif statementreplace

Hi, I got a little problem and I hoped someone can help me out.
When I have a matrix consisting of 3 columns, I want to replace a value in the third column if a row in the first column has a certain value. For example, I have the following matrix:
A =
     3     6     9
     2     6     8
     3     6     8
Lets call the first column x, the second y and the third z. Now what I want is that when x == 3, than z must become 20.
How can I do this?

Best Answer

Please try the following:
idx = A(:,1) == 3;
A(idx,3) = 20;
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