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;Viewing contents of file
;'/net/www/deutsch/idl/idllib/deutsch/misc/gauss2.pro'
;
;***********************************************************************
;+
;*NAME: GAUSS2
;*CLASS:
; numerical function
;*CATEGORY:
;
;*PURPOSE: TO CALCULATE A GAUSSIAN FUNCTION
;
;*CALLING SEQUENCE:
; GAUSS,X,X0,DX,YMAX,Y
;
;*PARAMETERS:
; X (REQ) (I) (0 1) (I L F D)
; required scalar or vector containing the independent variable(s)
;
; X0 (REQ) (I) (0) (F D)
; required scalar giving the center of the Gaussian function
; This parameter must have the same units as X.
;
; DX (REQ) (I) (0) (F D)
; required scalar giving the one sigma width of the distribution
; This parameter must have the same units as X.
;
; YMAX (REQ) (I) (0) (F D)
; the Gaussian value at the peak of the distribution
;
; Y (REQ) (O) (0 1) (F D)
; required output scalar or vector giving the calculated value
; of the gaussian from the expression:
; Y = YMAX * EXP (-0.5 * ((X-X0)/DX)^2)
;
;*EXAMPLES:
; To calculate a gaussian with center at 1545 A, sigma of 2 A, using the
; wavelength scale derived from an IUE spectrum, with amplitude 1.0,
;
; GAUSS,WAVE,1545.,2.,1.0,Y
;
;*SYSTEM VARIABLES USED:
; None
;
;*INTERACTIVE INPUT:
; None
;
;*SUBROUTINES CALLED:
; PARCHECK
;
;*FILES USED:
; None
;
;*SIDE EFFECTS:
; None
;
;*RESTRICTIONS:
; None
;
;*NOTES:
; Values for which (X-X0)/DX > 9 are set to zero.
; If DX = 0, the delta function is returned.
;
;*PROCEDURE:
; GAUSS is similiar to Bevingtons program PGAUSS (p.45)
;
;*MODIFICATION HISTORY:
; Aug 19 1979 I. Ahmad initial program
; Jul 7 1984 RWT GSFC updated documentation
; Sep 25 1984 RWT GSFC changed limit from 12 sigma to 9 sigma due to
; problems in WFIT. Also compiles PCHECK.
; Apr 13 1987 RWT GSFC add PARCHECK
; Aug 19 1987 RWT GSFC add procedure call listing
; Mar 9 1988 CAG GSFC add VAX RDAF-style prolog
; Nov 26 1990 JKF ACC copied to GHRS DAF
;-

;***********************************************************************
;function GAUSS2,X,X0,DX,YMAX,Y
pro GAUSS2,X,X0,DX,YMAX,Y
;
;
IF N_PARAMS(0) EQ 0 THEN BEGIN
PRINT,' GAUSS,X,X0,DX,YMAX,Y'
RETALL & END
IF DX NE 0 THEN BEGIN
ARG=(ABS((X-X0)/DX)<9.) ; set values 9 sigma to 0 to avoid trap errors
Y=EXP(-ARG*ARG/2)*(ARG LT 9.0)
END ELSE Y=(0.*X)*(X NE X0)+(X EQ X0)
; IF DX EQ 0 RETURN DELTA FUNCTION
Y=Y*YMAX
;RETURN,y
RETURN
END