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comparison scripts/statistics/base/qqplot.m @ 11436:e151e23f73bc

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Overhaul base statistics functions and documentation of same. Add or improve input validation. Add input validation tests. Add functional tests. Improve or re-write documentation strings.
author Rik <octave@nomad.inbox5.com>
date Mon, 03 Jan 2011 21:23:08 -0800
parents 95c3e38098bf
children fd0a3ac60b0e
comparison
equal deleted inserted replaced
11435:20f53b3a558f 11436:e151e23f73bc
16 ## You should have received a copy of the GNU General Public License 16 ## You should have received a copy of the GNU General Public License
17 ## along with Octave; see the file COPYING. If not, see 17 ## along with Octave; see the file COPYING. If not, see
18 ## <http://www.gnu.org/licenses/>. 18 ## <http://www.gnu.org/licenses/>.
19 19
20 ## -*- texinfo -*- 20 ## -*- texinfo -*-
21 ## @deftypefn {Function File} {[@var{q}, @var{s}] =} qqplot (@var{x}, @var{dist}, @var{params}) 21 ## @deftypefn {Function File} {[@var{q}, @var{s}] =} qqplot (@var{x})
22 ## @deftypefnx {Function File} {[@var{q}, @var{s}] =} qqplot (@var{x}, @var{dist})
23 ## @deftypefnx {Function File} {[@var{q}, @var{s}] =} qqplot (@var{x}, @var{dist}, @var{params})
22 ## Perform a QQ-plot (quantile plot). 24 ## Perform a QQ-plot (quantile plot).
23 ## 25 ##
24 ## If F is the CDF of the distribution @var{dist} with parameters 26 ## If F is the CDF of the distribution @var{dist} with parameters
25 ## @var{params} and G its inverse, and @var{x} a sample vector of length 27 ## @var{params} and G its inverse, and @var{x} a sample vector of length
26 ## @var{n}, the QQ-plot graphs ordinate @var{s}(@var{i}) = @var{i}-th 28 ## @var{n}, the QQ-plot graphs ordinate @var{s}(@var{i}) = @var{i}-th
27 ## largest element of x versus abscissa @var{q}(@var{i}f) = G((@var{i} - 29 ## largest element of x versus abscissa @var{q}(@var{i}f) = G((@var{i} -
28 ## 0.5)/@var{n}). 30 ## 0.5)/@var{n}).
29 ## 31 ##
30 ## If the sample comes from F except for a transformation of location 32 ## If the sample comes from F, except for a transformation of location
31 ## and scale, the pairs will approximately follow a straight line. 33 ## and scale, the pairs will approximately follow a straight line.
32 ## 34 ##
33 ## The default for @var{dist} is the standard normal distribution. The 35 ## The default for @var{dist} is the standard normal distribution. The
34 ## optional argument @var{params} contains a list of parameters of 36 ## optional argument @var{params} contains a list of parameters of
35 ## @var{dist}. For example, for a quantile plot of the uniform 37 ## @var{dist}. For example, for a quantile plot of the uniform
38 ## @example 40 ## @example
39 ## qqplot (x, "uniform", 2, 4) 41 ## qqplot (x, "uniform", 2, 4)
40 ## @end example 42 ## @end example
41 ## 43 ##
42 ## @noindent 44 ## @noindent
43 ## @var{dist} can be any string for which a function @var{dist_inv} 45 ## @var{dist} can be any string for which a function @var{distinv} or
44 ## that calculates the inverse CDF of distribution @var{dist} exists. 46 ## @var{dist_inv} exists that calculates the inverse CDF of distribution
47 ## @var{dist}.
45 ## 48 ##
46 ## If no output arguments are given, the data are plotted directly. 49 ## If no output arguments are given, the data are plotted directly.
47 ## @end deftypefn 50 ## @end deftypefn
48 51
49 ## Author: KH <Kurt.Hornik@wu-wien.ac.at> 52 ## Author: KH <Kurt.Hornik@wu-wien.ac.at>
53 56
54 if (nargin < 1) 57 if (nargin < 1)
55 print_usage (); 58 print_usage ();
56 endif 59 endif
57 60
58 if (! (isvector(x))) 61 if (!(isnumeric (x) && isvector(x)))
59 error ("qqplot: x must be a vector"); 62 error ("qqplot: X must be a numeric vector");
60 endif 63 endif
64
65 if (nargin == 1)
66 f = @stdnormal_inv;
67 else
68 if ( exist (invname = sprintf ("%sinv", dist))
69 || exist (invname = sprintf ("%s_inv", dist)))
70 f = str2func (invname);
71 else
72 error ("qqplot: no inverse CDF found for distribution DIST");
73 endif
74 endif;
61 75
62 s = sort (x); 76 s = sort (x);
63 n = length (x); 77 n = length (x);
64 t = ((1 : n)' - .5) / n; 78 t = ((1 : n)' - .5) / n;
65 if (nargin == 1)
66 f = @stdnormal_inv;
67 else
68 f = str2func (sprintf ("%s_inv", dist));
69 endif;
70 if (nargin <= 2) 79 if (nargin <= 2)
71 q = feval (f, t); 80 q = feval (f, t);
72 q_label = func2str (f); 81 q_label = func2str (f);
73 else 82 else
74 q = feval (f, t, varargin{:}); 83 q = feval (f, t, varargin{:});
75 if (nargin > 3) 84 if (nargin > 3)
76 tmp = sprintf (", %g", varargin{2:end}); 85 tmp = sprintf (", %g", varargin{2:end});
77 else 86 else
78 tmp = ""; 87 tmp = "";
79 endif 88 endif
80 q_label = sprintf ("%s with parameter(s) %g%s", func2str (f), 89 q_label = sprintf ("%s with parameter(s) %g%s",
81 varargin{1}, tmp); 90 func2str (f), varargin{1}, tmp);
82 endif 91 endif
83 92
84 if (nargout == 0) 93 if (nargout == 0)
85 plot (q, s); 94 plot (q, s);
86 xlabel (q_label); 95 xlabel (q_label);