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

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beginner
beginner 2016-3-23
编辑： Jos (10584) 2016-3-23
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.

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采纳的回答

random09983492
random09983492 2016-3-23
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).

更多回答（1 个）

Jos (10584)
Jos (10584) 2016-3-23
编辑：Jos (10584) 2016-3-23
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

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