Integrating with trapz and int

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Nico Pisani 2020-12-28

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评论： John D'Errico 2020-12-28

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Hi All.

I have the following code

syms theta 
B=dlmread('630nm in ARF E_y cartesian coordinates.txt')
B1new = B(:,1)
B2new=B(:,2)
alpha=sqrt(B2new.^2+B1new.^2)
BS=[alpha]
CS=[conj(B(:,3))]
k=2.*pi./(630.*0.000000001)
bess=[besselj(0,k.*BS.*sin(theta)).*tan(theta).*CS.*BS]
U=trapz(bess)
Bessint = int(U,theta,[0 0.6])
Fvpa = vpa(Bessint)

for calculating the following integral

CS, BS correspond respectively to \rho and E*(\pho) which are extracted from a .txt file.

The code has calculated symbolically U but after hours running it has not completed the Fvpa quantity calculation yet (editor reports "busy" status).

Matrices at stake are quite big (~40000 ins column)

May anyone help me please?

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John D'Errico 2020-12-28

Get a faster computer. Use smaller matrices, solve smaller problems. Get some coffee, read a book while you wait (something long, and preferably about numerical methods in MATLAB.) Or, ... write better code.

Note that it is rarely a good idea to use trapz AND int in the same code. trapz being a numerical integration method with relatively low accuracy makes little sense in conjunction with a symbolic tool.

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