Solving derivative in point takes to long

Question

Edlan Ih 2019-5-20

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/463101-solving-derivative-in-point-takes-to-long

回答： Walter Roberson 2019-5-20

Hi,

I have complex function which includes diagonalization on which i want to compute the derivative.

However if i try this using inline(diff()) command it gets stuck on busy. But if i try this on a simple function (x^2) it works.

How can i make i work for my complex function?

my derivative:

syms Lambda
derivitive = inline(diff(Steady_State(Lambda), Lambda),'Lambda')
derivitive(0.23)

my complex function:

function Beta = Steady_State(Lambda)
P0 = exp(-Lambda)
P1 = Lambda*exp(-Lambda)
P2 = (Lambda^(2)*exp(-Lambda)/2)
P3 = (Lambda^(3)*exp(-Lambda)/6)
b_NN = [100; 85; 75; 65; 55; 50; 45; 40; 35; 33; 31; 29; 27; 25; 23; 21.5; 20; 18.5; 17; 16; 15]
bonusmalus_NN = [1-P0,P0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,;
    1-P0,0,P0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    1-P0,0,0,P0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    1-P0,0,0,0,P0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    1-P0,0,0,0,0,P0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    1-P0,0,0,0,0,0,P0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    1-P0-P1,P1,0,0,0,0,0,P0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    1-P0-P1,0,P1,0,0,0,0,0,P0,0,0,0,0,0,0,0,0,0,0,0,0;
    1-P0-P1,0,0,P1,0,0,0,0,0,P0,0,0,0,0,0,0,0,0,0,0,0;
    1-P0-P1,0,0,0,P1,0,0,0,0,0,P0,0,0,0,0,0,0,0,0,0,0;
    1-P0-P1,0,0,0,0,P1,0,0,0,0,0,P0,0,0,0,0,0,0,0,0,0;
    1-P0-P1-P2,P2,0,0,0,0,P1,0,0,0,0,0,P0,0,0,0,0,0,0,0,0;
    1-P0-P1-P2,0,P2,0,0,0,0,P1,0,0,0,0,0,P0,0,0,0,0,0,0,0;
    1-P0-P1-P2,0,0,P2,0,0,0,0,P1,0,0,0,0,0,P0,0,0,0,0,0,0;
    1-P0-P1-P2,0,0,0,P2,0,0,0,0,P1,0,0,0,0,0,P0,0,0,0,0,0;
    1-P0-P1-P2,0,0,0,0,P2,0,0,0,0,P1,0,0,0,0,0,P0,0,0,0,0;
    1-P0-P1-P2-P3,P3,0,0,0,0,P2,0,0,0,0,P1,0,0,0,0,0,P0,0,0,0;
    1-P0-P1-P2-P3,0,P3,0,0,0,0,P2,0,0,0,0,P1,0,0,0,0,0,P0,0,0;
    1-P0-P1-P2-P3,0,0,P3,0,0,0,0,P2,0,0,0,0,P1,0,0,0,0,0,P0,0;
    1-P0-P1-P2-P3,0,0,0,P3,0,0,0,0,P2,0,0,0,0,P1,0,0,0,0,0,P0;
    1-P0-P1-P2-P3,0,0,0,0,P3,0,0,0,0,P2,0,0,0,0,P1,0,0,0,0,P0]
[V,A] = eig(bonusmalus_NN)
V_inv = inv(V)
p_lim = V*A^10000000*V_inv
p_lim = p_lim(1,:)
Beta = p_lim * b_NN
end

Can someone help me out?

Kind Regards

Edlan

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Walter Roberson 2019-5-20

Is it correct that you are using MATLAB 5.2 or earlier, with the Maple based Symbolic Toolbox? That is only reason that I can think of to try to use inline() with symbolic expressions.

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Answer 1

Walter Roberson 2019-5-20

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/463101-solving-derivative-in-point-takes-to-long#answer_375865

The language used by the symbolic toolbox has never been compatible with execution by taking the character version of a symbolic expression and executing it as matlab code. What you are doing has always had undefined results.

You should be using matlabFunction instead of inline.

Unless you are using MATLAB 5.2 or earlier you should stop using inline except as a novelty.