How do I add a column to a matrix with specific values?

If I have a matrix like so:

1 2 3 4
5 2 6 7 
3 6 5 7

How can I add a third column with a value of one for every row that has a value of 2 in the second column? Thanks!

Answer 1

[Z]

Never mind, I found out that this is the syntax:

mydata (mydata (:,2) == 2,4) = 1;

Answer 2

[Greg Heath]

The question is ill posed.

The matrix has 4 columns and the question is how to add a third column.

The accepted answer is incorrect.

It replaces components in the fourth column

1. Bad question

2. Bad answer.

It should be flagged.