Replace values in matrix with other values

Question

I have a matrix with integers and I need to replace all appearances of 2 with -5. What is the most efficient way to do it? I made it the way below, but I am sure there is mo

Answer 1

Try this:

a(a==2) = -5;

The somewhat longer version would be

ind_plain = find(a == 2);
a(ind_plain) = -5;

In other words, you can index a matrix directly using linear indexes, no need to convert them using ind2sub -- very useful! But as demonstrated above, you can get even shorter if you index the matrix using a boolean matrix.

By the way, you should put semicolons after your statements if (as is usually the case) you're not interested in getting the result of the statement dumped out to the console.