examples/deriv/basic

   1 #!/usr/bin/perl -w
   2 use strict;
   3 use Math::GSL::Deriv qw/:all/;
   4 use Math::GSL::Errno qw/:all/;
   5
   6 # This is a numerical verification of the mathematical fact
   7 # that the derivative of sin(x) is cos(x), i.e.
   8 #
   9 #  d
  10 #  -( sin(x) ) = cos(x)
  11 #  dx
  12
  13 my ($x, $h) = (1.5, 0.01);
  14 my ($status, $val,$err) = gsl_deriv_central ( sub {  sin($_[0]) }, $x, $h);
  15 my $res = abs($val - cos($x));
  16 if ($status == $GSL_SUCCESS) {
  17     printf "deriv(sin((%g)) = %.18g, max error=%.18g\n", $x, $val, $err;
  18     printf "       cos(%g)) = %.18g, residue=  %.18g\n"  , $x, cos($x), $res;
  19 } else {
  20     my $gsl_error = gsl_strerror($status);
  21     print "Numerical Derivative FAILED, reason:\n $gsl_error\n\n";
  22 }
  23