Comparing sets of data

I have a column of data that has a bunch of numbers indicating height of something. I have another column of data also indicating the height of something (they both have the same number of values). I want to say for every time a value in column X = 0, change the value that was in Y at the same location to 0.

I am not sure how to do this. Maybee an IF statement?

Answer 1

[Fangjun Jiang]

x=round(rand(10,1));
y=1:10;
index=x==0;
y(index)=0;