;;; PLT Scheme Science Collection
;;; random-distributions/gaussian-graphics.ss
;;; Copyright (c) 2004 M. Douglas Williams
;;;
;;; This library is free software; you can redistribute it and/or
;;; modify it under the terms of the GNU Lesser General Public
;;; License as published by the Free Software Foundation; either
;;; version 2.1 of the License, or (at your option) any later version.
;;;
;;; This library is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;;; Lesser General Public License for more details.
;;;
;;; You should have received a copy of the GNU Lesser General Public
;;; License along with this library; if not, write to the Free
;;; Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
;;; 02111-1307 USA.
;;;
;;; -------------------------------------------------------------------
;;;
;;; This code implements graphics for Gaussian distributions.
;;;
;;; Version  Date      Description
;;; 0.1.0    08/07/04  This is the initial release of the Guassian
;;;                    distribution graphics routines. (Doug Williams)
;;; 1.0.0    09/28/04  Added contracts for functions.  Marked as ready
;;;                    for Release 1.0.  (Doug Williams)

(module gaussian-graphics mzscheme
  
  (require (lib "contract.ss"))
  
  (provide/contract
   (gaussian-plot
    (-> real? (>=/c 0.0) any))
   (unit-gaussian-plot
    (-> any)))
  
  (require "gaussian.ss")
  (require (lib "plot.ss" "plot"))
  
  ;; gaussian-plot: real x real -> void
  ;; Plot the pdf and cdf for a gaussian distribution with the given
  ;; mean and standard deviation.  The x axis range is +/- three sigma
  ;; around the mean.
  (define (gaussian-plot mu sigma)
    (plot (mix (line (lambda (x) (gaussian-pdf x mu sigma))
                     (color 'red))
               (line (lambda (x) (gaussian-cdf x mu sigma))
                     (color 'blue)))
          (x-min (+ mu (* -3 sigma)))
          (x-max (+ mu (* 3 sigma)))
          (y-min 0) (y-max 1)
          (y-label "Density")
          (title "Gaussian Distribution")))
  
  ;; unit-gaussian-plot: -> void
  ;; Plot the pdf and cdf for a unit gaussian distribution (standard
  ;; normal distribution).  The x axis range is +/- three.
  (define (unit-gaussian-plot)
    (plot (mix (line unit-gaussian-pdf (color 'red))
               (line unit-gaussian-cdf (color 'blue)))
          (x-min -3) (x-max 3)
          (x-label "x")
          (y-min 0) (y-max 1)
          (y-label "Density")
          (title "Unit Gaussian Distribution")))
  
)