issue in boolean variable in matlab

I have two vectors A and B of the same size.I have the following code.

 y1=[];y2=[];y3=[];y4=[];
 for i=1:length(A)
 for k=0:0.1:1
        for m=0:0.1:1
           h=k*m/(k+m-k*m);
           if(h==A(i))
                y1=[y1 k];
                y2=[y2 m];
           end
           if(h==B(i))
                y3=[y3 k];
                y4=[y4 m];
           end

        end
    end
    end

This code runs fine. But in this code say for example if h=A(i)=0.2 is true. Then y1 and y2 can only take the combinations [0,0.2],[0.2,0]

If h=B(i)=0.4 is true then y3 and y4 can take combinations[0,0.04],[0.02,0.02],[0.01,0.03] likewise. I want to group all the combinations of B for a particular A(i) and to know when A(i) takes a different value, and for that different A(i) the corresponding B(j)'s.

So I wrote the following code.

y1=[];y2=[];y3=[];y4=[];
for i=1:length(A)
    istrue=0; 
    for k=0:0.01:1
           for m=0:0.01:1
           h=k*m/(k+m-k*m);

       if(h==A(i))
            istrue=1;
            y1=[y1 k];
            y2=[y2 m];
       end

       if(istrue==1)

           if(h==B(i))

               y3=[y3 k];
               y4=[y4 m];
           end
       end
       istrue=0;

    end
end
end  

But the problem is this never executes the part

               if(h==B(i))

                   y3=[y3 k];
                   y4=[y4 m];
               end  

If I remove istrue variable and run as in the previous code it works.

if(h==A(i))
                    istrue=1;
                    y1=[y1 k];
                    y2=[y2 m];
               end

gets executed at least once. Yet the part

if(h==B(i))


                   y3=[y3 k];
                   y4=[y4 m];
               end `   

doesn't get executed.
What is wrong with my code?Is the issue with the istruevariable?