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I'm trying to use MATLAB Bessel function of zeroth order ---> besselj(0,Z). What I noticed is: it can handle real part of nth power (say e100) but not imaginary part if it is greater than (e2) in a complex argument.

Eg: (2+2*i) complex argument it will handle. But it can't handle (20000+20000*i)-----> gives answer as "infinity".

this is what i get :

besselj(0,2e4+i*2e4)

ans =

   Inf

Can some one explain this? Is there any limit of the power in the imaginary part?

Lundin
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matrix
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1 Answers1

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From Bessel function page on wikipedia, middle of the page, there is a formula for asymptotic expansion for large complex number with known imaginary part. This expansion has a term of the form exp(abs(imag(z)))*O(1/abs(z)), (O is the O-notation), so it grows very rapidly with the imaginary part of the input number.

Bentoy13
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  • Thanks Bentoy for replying. So, this means there should be a limit. My program/values are in the range (e3) So, whatever I try it is giving infinity value. How can I proceed then? Is there any other method to overcome this? – matrix Jan 14 '15 at 06:54