Using 'fzero' in a for loop

Question

Jon Stapchuck 2021-4-26

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/813955-using-fzero-in-a-for-loop

评论： Jon Stapchuck 2021-4-26

Hello,

I am trying to solve for the roots within a 'for loop', and within the function for which I am root finding, I am using a previously defined variable.

It might make it easier to show my code:

A_Astar_x = zeros(1,IL-1);
Mach_Test = zeros(1,IL-1);
M_x = zeros(1,IL-1);
for i=1:IL-1
    A_Astar_x(i) = (y(i,JL)-y(i,1))/(y(1,JL)-y(1,1))*A_A;
    Mach_Test(i) = @(set)  A_Astar_x(i)-(1/set)*((1+.5*(gamma-1)*set^2)/(.5*(gamma+1))).^alpha;
    M_x(i) = fzero(Mach_Test(i),.2);
end

I get an error message that says:

Conversion to double from function_handle is not possible.

Does this error message mean that I cannot solve for the roots iteratively like this?

If not, does anyone know any other methods to go about this?

Thanks,

Jon

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Answer 1

Matt J 2021-4-26

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/813955-using-fzero-in-a-for-loop#answer_685420

编辑：Matt J 2021-4-26

在 MATLAB Online 中打开

Do you really need to save the sequences of anything besides the M_x(i)? If not, then,

for i=1:IL-1
    
    A_Astar_x = (y(i,JL)-y(i,1))/(y(1,JL)-y(1,1))*A_A;
    Mach_Test = @(set)  A_Astar_x-(1/set)*((1+.5*(gamma-1)*set^2)/(.5*(gamma+1))).^alpha;
    
    M_x(i) = fzero(Mach_Test,.2);
end

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Jon Stapchuck 2021-4-26

That solved it, thank you.

I didn't realize you didn't have to save everything unless you plan to actually use it, but that makes a lot of sense. Probably is more efficient as well.

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