make zero some rows of a matrix

It's neede to make zero those rows of a matrix that matrix(i,2) is 2 value less than matrix(1,2). 'matrix' has 2 column and 10000 rows. I wrote this but i don't know for what doesn't work

for i=1:size(r,1)
    if r(i,2)-r(1,2)<2
        r(i,2)=0;
    end
end

[Wayne King]

I'm not sure I understand the condition you want to test correctly, because assume that r(1,2)=6 and r(i,2)=5 for some i not equal to 1. Then,

r(i,2)-r(1,2)<1 is true (5-6 < 1), but r(i,2) is not "2 value less than r(1,2)".

So what exactly do you want to test?

[mohammad]

edit

sorry there was a typing wrong

Answer 1

[Andrei Bobrov]

r(r(1,2)-r(:,2)>=2,:) = 0

[mohammad]

really nice

thanks

[mohammad]

i don't know but when i equal a=r(1,2) and use a instead of r(1,2), matlab works!