Replace certain values of matrix by one single value

Hi I'm relatively new to Matlab.. I would like to know how to generate a matrix B that replaces all components of a matrix A (which is a 100x100 randomly generated matrix) lying between 2.9 and 3.2, by -1. I also tried using the for loop but it wouldn't work.

 for i=1:100;
    j=1:100;
    if A(i,j)==2.9:3.2;
        A(i,j)=-1;
    end
end

Thanks a lot!!!

Answer 1

[Azzi Abdelmalek]

EDIT

B=A
B(B>2.9 & B<3.2)=-1

[Walter Roberson]

 B(2.9<B & B<3.2) = -1;

[rox]

thanks a lot! worked greatly :)