array length is not what I've set...

Hi,

This is my code, it works just fine, just I dont understand why my array Hopt_new is generating more arrays than I set.

Bo=1;
X = 0:0.1:3;

Hopt_new = zeros([1 90]);
h0_new = 0;
for j = 90:1:179
theta = j*pi/180;
handle = @(h0) test2fun(h0, theta, Bo,X);
Hopt_new(j)=fsolve(handle, h0_new);
h0_new = Hopt_new(j);

end

Why does Hopt_new have length of 179 instead of 90, which I set before the for loop? Is this because j goes until 179? I mean j actually is a "vector" with length of 90. I just dont get it.

Thanks a lot.

[Jos (10584)]

Yes, take a look at this code, and then see my answer:

A = [1 2 3]
A(6) = 99

Answer 1

[random09983492]

The first time the loop executes it sets Hopt_new(90).

The second time it sets Hopt_new(91).

If you want to start at the first index of Hopt_new, assign Hopt_new(j-89) rather than just Hopt_new(j).

Answer 2

[Jos (10584)]

In your code, the variable j has two roles:

1. an index into Hopt
2. a value that is used for calculation (angle?)

Your best option is to disentangle these using two variables:

Bo = 1;
X = 0:0.1:3;
Hopt_new = zeros([1 90]);
h0_new = 0;
Angle = 90:1:179 ;
for j2 = 1:numel(Angle)
    % loop over all angles
    theta = Angle(j2) * pi/180;
    handle = @(h0) test2fun(h0, theta, Bo, X);
    Hopt_new(j2) = fsolve(handle, h0_new);
    h0_new = Hopt_new(j2);
end