Subscripted assignment dimension mismatch. Error in main (line 17) [y(:,6), a6] = curvepoly(​x_heun,y_h​eun,6);

this worked for me fine yesterday, I haven't changed anything and today it says Subscripted assignment dimension mismatch.

Error in main (line 17)
        [y(:,6), a6] = curvepoly(x_heun,y_heun,6);

Why? and how do I fix it?

fx = inline('(y - ((y.^2)./x)./x)','x','y');

x0 = 1;
xf = 5;
y0 = 1;
tol = 0.001;
N = [1:0.1:5];

      for i = 1:length(N)

          [y_heun, x_heun] = Heun(fx,x0,xf,y0,N(i),tol);

          [y(:,2), a2] = curvepoly(x_heun,y_heun,2);

      end

function [y,a] = curvepoly(x_heun,y_heun,order)

j = order;

for k = 1:j + 1;
    for i = 1:j + 1;
        A(k,i) = sum(x_heun.^((k+i-2)));
    end
end

for i = 1:j + 1;
    B(i,:) = sum(y_heun.*x_heun.^(i-1));
end

a = inv(A)*B;
y = 0;

for i = 1:j+1
    y = y+a(i).*x_heun.^(i-1);
end

Answer 1

[Matt J]

The line in your error message does not appear in your code. I do see the rather similar line

[y(:,2), a2] = curvepoly(x_heun,y_heun,2);

which makes rather little sense within a loop over i, since it will just repeatedly overwrite y(:,2) and a2.

Perhaps that's what you changed.

[Matt J]

Aside from that, your function curvepoly returns a vector of length order+1. If size(y,1) does not match this, it would result in the error you've shown.