kjb_bessel_I0 - Computes modified Bessel function, order 0


#include "wrap_gsl/wrap_gsl_sf.h"

Example compile flags (system dependent):
   -L/home/kobus/misc/load/linux_x86_64_opteron -L/usr/lib/x86_64-linux-gnu
  -lKJB                               -lfftw3  -lgsl -lgslcblas -ljpeg  -lSVM -lstdc++                    -lpthread -lSLATEC -lg2c    -lacml -lacml_mv -lblas -lg2c      -lncursesw 

int kjb_bessel_I0
	double *P_ptr,
	double x


double *P_ptr
Pointer to where the result should be stored
double x
Value at which to evaluate erf


If possible, computes the modified Bessel function, order 0, usually denoted by something like I_0(x). This is defined as I_0(x) = i * J_0(i*x), where J_0 is the ordinary Bessel function, order 0, and little i is the imaginary unit. This routine is a thin wrapper to GSL code that computes this special function. If the GSL library is not available, this routine fails with a return value of ERROR. Otherwise, the value is returned in the location pointed to by pointer P_ptr, which must not equal null. The argument to the function is stored in x. Keep in mind that I_0(x) grows very quickly with increasing x, on the order of exp(x)/sqrt(x). If you need to compute I_0 for a large value (perhaps in a ratio calculation), please consider using kjb_scaled_bessel_I0() instead. In this context if x has three digits, it is LARGE.


If successful, the value is written to *P_ptr and this function returns NO_ERROR. If the routine fails -- caused by the library being unavailable during linking -- an error message is set and the return value is ERROR.


This software is not adequatedly tested. It is recomended that results are checked independantly where appropriate.


Andrew Predoehl


Andrew Predoehl


kjb_erf , kjb_scaled_bessel_I1 , kjb_scaled_bessel_I0