Mercurial > octave
view scripts/statistics/base/ppplot.m @ 3426:f8dde1807dee
[project @ 2000-01-13 08:40:00 by jwe]
author | jwe |
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date | Thu, 13 Jan 2000 08:40:53 +0000 |
parents | 781c930425fd |
children | 71d2e09c15a2 |
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## Copyright (C) 1995, 1996, 1997 Kurt Hornik ## ## This program is free software; you can redistribute it and/or modify ## it under the terms of the GNU General Public License as published by ## the Free Software Foundation; either version 2, or (at your option) ## any later version. ## ## This program 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 ## General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with this file. If not, write to the Free Software Foundation, ## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. ## usage: [p, y] = ppplot (x [, dist [, params]]) ## ## Performs a PP-plot (probability plot). ## ## If F is the CDF of the distribution `dist' with parameters `params' ## and x a sample vector of length n, the PP-plot graphs ordinate y(i) = ## F (i-th largest element of x) versus abscissa p(i) = (i - 0.5)/n. If ## the sample comes from F, the pairs will approximately follow a ## straight line. ## ## The default for `dist' is the standard normal distribution. The ## optional argument `params' contains a list of parameters of ## `dist'. E.g., for a probability plot of the uniform distribution on ## [2,4] ans x, use `ppplot (x, "uniform", 2, 4)'. ## ## If no output arguments are given, the data are plotted directly. ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at> ## Description: Perform a PP-plot (probability plot) function [p, y] = ppplot (x, dist, ...) if (nargin < 1) usage ("ppplot (x [, dist [, params]])"); endif if !is_vector (x) error ("ppplot: x must be a vector."); endif s = sort (x); n = length (x); p = ((1 : n)' - 0.5) / n; if (nargin == 1) F = "stdnormal_cdf"; else F = sprintf ("%s_cdf", dist); endif; if (nargin <= 2) y = feval (F, s); else y = feval (F, s, all_va_args); endif if (nargout == 0) axis ([0, 1, 0, 1]); set nokey; plot (p, y); endif endfunction