#======================================================================

#                    A N T S F I L T E R S . P L 

#                    doc: Sun Mar 14 15:17:29 1999

#                    dlm: Wed Feb 13 11:11:16 2013

#                    (c) 1999 A.M. Thurnherr

#                    uE-Info: 38 97 NIL 0 0 72 2 2 4 NIL ofnI

#======================================================================

# HISTORY:

#	Mar 14, 1999: - created for filters

#	Dec 11, 1999: - made &antsXCheck() return mean dx

#				  - BUG: dx was calculated independently of from val

#	Mar 31, 2004: - added $fac optional param

#	Jul  1, 2006: - Version 3.3 [HISTORY]

#	Jan  5, 2011: - BUG: did not work for -ve dx

# Implement commonly used fuctions for filters (but not worth including

# into [./antsutils.pl] because of efficiency considerations)

{ my($dx) = 0;										# static vars

sub antsXCheck($$$) # ($xfnr,$from,$to,$fac) -> mean dx	# sanity check on @ants_

{

	my($xfnr,$from,$to,$fac) = @_;

	my($cdx,$r,$sdx);

	$fac = 2 unless defined($fac);

	unless ($dx) {									# find goal dx

		croak("$0: can't handle nan (x field)\n")

			unless (numberp($ants_[0][$xfnr]) && numberp($ants_[1][$xfnr]));

		$dx = $ants_[$from+1][$xfnr] - $ants_[$from][$xfnr];

	}

	for ($r=$from+1; $r <= $to; $r++) {

		croak("$0: can't handle $ants_[$r][$xfnr] (x field)\n")

			unless (numberp($ants_[$r][$xfnr]));

		$cdx = $ants_[$r][$xfnr] - $ants_[$r-1][$xfnr];

		croak(sprintf("$0: input badly non-uniformly spaced: @ rec#%d dx=%g, %.1fx target dx=%g\n",

						$r,$cdx,$cdx/$dx,$dx))

			if (($dx > 0) && ($cdx > $fac*$dx || $cdx < $dx/$fac)) ||

			   (($dx < 0) && ($cdx < $fac*$dx || $cdx > $dx/$fac));

		$sdx += $cdx;

	}

	return $sdx/($to-$from);

}

} # end of $dx static scope

1;