Your original for-loop probably was incorrect. And why do you want a while loop? You already know how many iterations you want.
A = (1:10)';
B= rand(10,2);
C= A; C(:,2:3)= B;
Y= B(:,2);
X= B(:,1);
for i= 1:size(B,1)
% ^ are you sure that shouldn't be C instead?
C(i,4)= sin(C(i,3)/sin(C(i,2)));
end
In this case you can avoid the loop entirely:
C(:,4)=sin( C(:,3) ./ sin( C(:,2) ) );
And are you sure you mean this, and not this?
C(:,4)=sin( C(:,3) ) ./ sin( C(:,2) );
