gauss1p.pro
2.19 KB
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;+
; NAME:
; GAUSS1P
;
; AUTHOR:
; Craig B. Markwardt, NASA/GSFC Code 662, Greenbelt, MD 20770
; craigm@lheamail.gsfc.nasa.gov
;
; PURPOSE:
; Compute Gaussian curve given the mean, sigma and area (procedure).
;
; MAJOR TOPICS:
; Curve and Surface Fitting
;
; CALLING SEQUENCE:
; GAUSS1, XVALS, [MEAN, SIGMA, AREA], YVALS, SKEW=skew
;
; DESCRIPTION:
;
; This routine computes the values of a Gaussian function whose
; X-values, mean, sigma, and total area are given. It is meant to be
; a demonstration for curve-fitting.
;
; XVALS can be an array of X-values, in which case the returned
; Y-values are an array as well. The second parameter to GAUSS1
; should be an array containing the MEAN, SIGMA, and total AREA, in
; that order.
;
; INPUTS:
; X - Array of X-values.
;
; [MEAN, SIGMA, AREA] - the mean, sigma and total area of the
; desired Gaussian curve.
;
; YVALS - returns the array of Y-values.
;
;
; KEYWORD PARAMETERS:
;
; SKEW - You may specify a skew value. Default is no skew.
;
; EXAMPLE:
;
; p = [2.2D, 1.4D, 3000.D]
; x = dindgen(200)*0.1 - 10.
; gauss1p, x, p, y
;
; Computes the values of the Gaussian at equispaced intervals
; (spacing is 0.1). The gaussian has a mean of 2.2, standard
; deviation of 1.4, and total area of 3000.
;
; REFERENCES:
;
; MODIFICATION HISTORY:
; Transcribed from GAUSS1, 13 Dec 1999, CM
; Added copyright notice, 25 Mar 2001, CM
;
; $Id: gauss1p.pro,v 1.2 2001/03/25 18:55:12 craigm Exp $
;
;-
; Copyright (C) 1999,2001, Craig Markwardt
; This software is provided as is without any warranty whatsoever.
; Permission to use, copy, modify, and distribute modified or
; unmodified copies is granted, provided this copyright and disclaimer
; are included unchanged.
;-
pro gauss1p, x, p, f, skew=skew, _EXTRA=extra
sz = size(x)
if sz(sz(0)+1) EQ 5 then smax = 26D else smax = 13.
if n_elements(p) GE 3 then norm = p(2) else norm = x(0)*0 + 1
u = ((x-p(0))/(abs(p(1)) > 1e-20))^2
mask = u LT (smax^2) ;; Prevent floating underflow
f = norm * mask * exp(-0.5*temporary(u) * mask) / (sqrt(2.D * !dpi)*p(1))
mask = 0
if n_elements(skew) GT 0 then $
f = (1.D + skew * (x-p(0))/p(1))*f
return
end