This code plot nothing and i don't understand why ?!

    i=1;
    j=1;
    x=y1(:,2);
    u=y1(:,4);
    figure
    while (i<= size(x)& j<=size(u))

       vv= x(i)*sin(u(j));
       xx= x(i)*(1-cos(u(j)));
       hold on
        plot(vv,xx,'r');
        i= i+1;
        j= j+1;
    end

Answer 1

[the cyclist]

My guess is that size(x) is going to be something like

 [7 1]

so i is not less than that. I think maybe you want length(x) or numel(x) instead of size(x).

[Omar]

thanks alot

Answer 2

[James Tursa]

size(x) and size(u) are vectors, so i<= size(x)& j<=size(u) is a vector result, which is not what you likely intended. Try using numel instead so that it is a scalar expression. E.g.,

while (i<= numel(x) && j<=numel(u))

Also, you might want to specify a dot in the plot command:

plot(vv,xx,'r.');

[Omar]

thanks alot