# How can I calculate integral?

조회 수: 4 (최근 30일)
Serhat . 2012년 9월 18일
Hi all, I am new to matlab. I am using matlab R2012. I am trying to calculate this integral:
sigmaZ=rand(4,4); syms theta; Ps = 1/pi*(int(1./(det( (sigmaZ./(sin(theta)).^2 + eye(4)))),theta,0,pi/2));
It gives this error message:
?? The following error occurred converting from sym to double: Error using ==> mupadmex Error in MuPAD command: DOUBLE cannot convert the input expression into a double array.
If the input expression contains a symbolic variable, use the VPA function instead.
What is the problem here? Can you help me?
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Alexander 2012년 9월 18일
That's strange, I don't get that error. I do get this warning:
Warning: Explicit integral could not be found.
Sorry, no idea why this is happening.

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### 채택된 답변

Andrei Bobrov 2012년 9월 18일
편집: Andrei Bobrov 님. 2012년 9월 18일
sigmaZ=rand(4,4);
f = @(theta)1./(arrayfun(@(x)det(sigmaZ/sin(x).^2 + eye(4)),theta));
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Javier 2012년 9월 18일
It gives me no solution.
f = @(theta)1./(arrayfun(@(x)det(((sigmaZ/sin(x).^2 + eye(4)).^-1)*exp((sin(x).^2*eye(4)).^-1)),theta));

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### 추가 답변 (1개)

Javier 2012년 9월 18일
Hello Serhat
I dont understand well the integral expression and limits of integration. To solve numerically integrals in MatlabR 2012a (or previous version).
Create a function with the integral expression.
f=@(x)(x.^2)
Next, use qaudl function (in the command window type: doc quadl)
Value=quadl(f,0,1) % 0 and 1 are the limits of integration of f
Hope it helps. Best regards and welcome to Matlab world.
javier

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