How to change particular element of a matrix by comparing with a scalar value?

i have a code and its not working:

 a=rand(4,10);
 b=round(a);
 y=[1 3];
%only the y rows of a will be checking for condition
 beta1=0.30;
 if a<=beta1 %beta1 is less than equal a, b will change if its 1 will become 0 and viceversa
  b(y,:)=~b(y,:);
 end 
its not happening...plz plz help me out...

Answer 1

[Andrei Bobrov]

try

a=rand(4,10);
b=round(a);
y=[1 3];
beta1=0.30;

c = b(y,:)
t = a(y,:) <= beta1;
c(t) = ~c(t);
b(y,:) = c;

[suchismita]

thank u so much....