Mercurial > hg > octave-nkf
annotate scripts/statistics/base/qqplot.m @ 14570:d07d96e53612 stable
seconds after the minute can be 0-60, not 0-61
* system.txi (Timing Utilities): Correct possible values for number of
seconds in time structures. From Rafael Arndt <rafaelarndt@gmail.com>.
| author | John W. Eaton <jwe@octave.org> |
|---|---|
| date | Tue, 17 Apr 2012 14:42:49 -0400 |
| parents | 72c96de7a403 |
| children | 5d3a684236b0 |
| rev | line source |
|---|---|
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1 ## Copyright (C) 1995-2012 Kurt Hornik |
| 3426 | 2 ## |
| 3922 | 3 ## This file is part of Octave. |
| 4 ## | |
| 5 ## Octave is free software; you can redistribute it and/or modify it | |
| 6 ## under the terms of the GNU General Public License as published by | |
| 7016 | 7 ## the Free Software Foundation; either version 3 of the License, or (at |
| 8 ## your option) any later version. | |
| 3426 | 9 ## |
| 3922 | 10 ## Octave is distributed in the hope that it will be useful, but |
| 3200 | 11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 3426 | 13 ## General Public License for more details. |
| 14 ## | |
| 3200 | 15 ## You should have received a copy of the GNU General Public License |
| 7016 | 16 ## along with Octave; see the file COPYING. If not, see |
| 17 ## <http://www.gnu.org/licenses/>. | |
| 3200 | 18 |
| 3453 | 19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {[@var{q}, @var{s}] =} qqplot (@var{x}) |
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21 ## @deftypefnx {Function File} {[@var{q}, @var{s}] =} qqplot (@var{x}, @var{dist}) |
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22 ## @deftypefnx {Function File} {[@var{q}, @var{s}] =} qqplot (@var{x}, @var{dist}, @var{params}) |
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23 ## @deftypefnx {Function File} {} qqplot (@dots{}) |
| 3453 | 24 ## Perform a QQ-plot (quantile plot). |
| 3200 | 25 ## |
| 3453 | 26 ## If F is the CDF of the distribution @var{dist} with parameters |
| 27 ## @var{params} and G its inverse, and @var{x} a sample vector of length | |
| 28 ## @var{n}, the QQ-plot graphs ordinate @var{s}(@var{i}) = @var{i}-th | |
| 29 ## largest element of x versus abscissa @var{q}(@var{i}f) = G((@var{i} - | |
| 30 ## 0.5)/@var{n}). | |
| 3200 | 31 ## |
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32 ## If the sample comes from F, except for a transformation of location |
| 3200 | 33 ## and scale, the pairs will approximately follow a straight line. |
| 34 ## | |
| 3453 | 35 ## The default for @var{dist} is the standard normal distribution. The |
| 36 ## optional argument @var{params} contains a list of parameters of | |
| 37 ## @var{dist}. For example, for a quantile plot of the uniform | |
| 38 ## distribution on [2,4] and @var{x}, use | |
| 39 ## | |
| 40 ## @example | |
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41 ## qqplot (x, "unif", 2, 4) |
| 3453 | 42 ## @end example |
| 3200 | 43 ## |
| 6754 | 44 ## @noindent |
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45 ## @var{dist} can be any string for which a function @var{distinv} or |
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46 ## @var{dist_inv} exists that calculates the inverse CDF of distribution |
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47 ## @var{dist}. |
| 6754 | 48 ## |
| 3200 | 49 ## If no output arguments are given, the data are plotted directly. |
| 3453 | 50 ## @end deftypefn |
| 3200 | 51 |
| 5428 | 52 ## Author: KH <Kurt.Hornik@wu-wien.ac.at> |
| 3456 | 53 ## Description: Perform a QQ-plot (quantile plot) |
| 3200 | 54 |
| 3979 | 55 function [q, s] = qqplot (x, dist, varargin) |
| 3426 | 56 |
| 3200 | 57 if (nargin < 1) |
| 6046 | 58 print_usage (); |
| 3200 | 59 endif |
| 3426 | 60 |
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61 if (!(isnumeric (x) && isvector(x))) |
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62 error ("qqplot: X must be a numeric vector"); |
| 3200 | 63 endif |
| 64 | |
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65 if (nargin == 1) |
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66 f = @stdnormal_inv; |
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67 else |
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68 if ( exist (invname = sprintf ("%sinv", dist)) |
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69 || exist (invname = sprintf ("%s_inv", dist))) |
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70 f = str2func (invname); |
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71 else |
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72 error ("qqplot: no inverse CDF found for distribution DIST"); |
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73 endif |
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74 endif; |
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75 |
| 3200 | 76 s = sort (x); |
| 77 n = length (x); | |
| 78 t = ((1 : n)' - .5) / n; | |
| 79 if (nargin <= 2) | |
| 80 q = feval (f, t); | |
| 4348 | 81 q_label = func2str (f); |
| 3200 | 82 else |
| 5153 | 83 q = feval (f, t, varargin{:}); |
| 84 if (nargin > 3) | |
| 85 tmp = sprintf (", %g", varargin{2:end}); | |
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86 else |
| 5153 | 87 tmp = ""; |
| 88 endif | |
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89 q_label = sprintf ("%s with parameter(s) %g%s", |
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90 func2str (f), varargin{1}, tmp); |
| 3200 | 91 endif |
| 3426 | 92 |
| 3200 | 93 if (nargout == 0) |
| 6447 | 94 plot (q, s); |
| 3200 | 95 xlabel (q_label); |
| 96 ylabel ("sample points"); | |
| 97 endif | |
| 98 | |
| 99 endfunction |