vpasolve in for loop

Question

maedeh Gh 2019-2-19

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/445880-vpasolve-in-for-loop

评论： Etsuo Maeda 2019-3-5

I Run this code and it works correctly, but I wanna stop the for loop when it gets Empty sym: 0-by-1

for p=0:10
    ub= vpasolve(function==0,x,[1000*p,1000*(p+1)])
end

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Answer 1

Etsuo Maeda 2019-3-5

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https://ww2.mathworks.cn/matlabcentral/answers/445880-vpasolve-in-for-loop#answer_363828

在 MATLAB Online 中打开

"vpasolve" returns numerical values. Its output "ub" cannot be a sym variable. If you use "solve", you can use "isempty" and "break" for your pourpose.

syms x
for k = 1:2
    out = solve(x^k + 1 == 0, x)
    if isempty(out) == 1
        disp('break')
        break;
    end
    disp('in loop')
end

HTH

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Walter Roberson 2019-3-5

This is not quite correct. vpasolve() returns symbolic values that represent numeric values. They are sym, and when no solution is found then the empty sym can be returned.

Also there is no need to compare isempty() to 1: you can just test if isempty(out)

Etsuo Maeda 2019-3-5