#lang scheme/base
;;; PLT Scheme Science Collection
;;; random-distributions/chi-squared-graphics.ss
;;; Copyright (c) 2004-2008 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 chi-squared distributions.
;;;
;;; Version  Date      Description
;;; 0.1.0    09/17/04  This is the initial release of the chi-squared
;;;                    distribution graphics routines. (Doug Williams)
;;; 1.0.0    09/28/04  Added contracts for functions.  Marked as ready
;;;                    for Release 1.0.  (Doug Williams)
;;; 1.1.0    02/09/06  Added cdf.  (Doug Williams)
;;; 2.0.0    11/19/07  Changed calls to unchecked versions.
;;;                    (Doug Williams)
;;; 3.0.0    06/09/08  Changes required for V4.0.  (Doug Williams)
;;; 3.0.1    07/01/08  Changes x axis label.  (Doug Williams)

(require (lib "contract.ss"))

(provide/contract
 (chi-squared-plot
  (-> real? any)))

(require "chi-squared.ss")
(require (lib "plot.ss" "plot"))

(define (chi-squared-plot nu)
  (plot (mix (line (lambda (x) (unchecked-chi-squared-pdf x nu))
                   (color 'red))
             (line (lambda (x) (unchecked-chi-squared-cdf x nu))
                   (color 'blue)))
        (x-min 0.0) (x-max 10.0)
        (x-label "X")
        (y-min 0) (y-max 1)
        (y-label "Density")
        (title "Chi-Squared Distribution")))