Re: Assignment 2: problem 4.17

Ed Casas (edc@ece.ubc.ca) Mon, 31 Jan 2000 12:50:59 -0800 

Date: Mon, 31 Jan 2000 12:50:59 -0800
From: Ed Casas <edc@ece.ubc.ca>
Subject: Re: Assignment 2: problem 4.17



> I have a question about this problem? How can we plot the pdf
> and cdf without knowing the Io (the modified Bessel function)?

You have a number of options:

(1) If are creating your plot using Matlab (e.g. you have an ECE
Unix account) you can use the function:

        besseli(0,x)

If you prefer Mathcad, Mathematica or Maple, they have equivalent
functions (if you don't know how to use one of these programs,
now's probably a good time to learn).

(2) If you are using Excel you can use the besseli() function
(included in the Engineering functions).

(3) Your calculator may be able to compute the modified bessel
function.

(4) You can find the bessel function tabulated in handbooks of
mathematical functions, for example, Abramowitz and Stegun.

(5) If you want to do things the hard way, you can get the C source
code for the modified Bessel functions and an explanation of how
the routines are written from:

        http://lib-www.lanl.gov/numerical/bookcpdf/c6-5.pdf

or the SLATEC code in FORTRAN (which you can compile on some Unix
system via f2c):

	http://www.netlib.org/cgi-bin/netlibfiles.pl?filename=slatec/fnlib/besi0.f

-- 
Ed Casas   edc@ece.ubc.ca   http://casas.ece.ubc.ca   +1 604 822-2592