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qqplot

PURPOSE ^

% Perform a QQ-plot (quantile plot).

SYNOPSIS ^

function [q, s] = qqplot (x, dist, varargin)

DESCRIPTION ^

% -*- texinfo -*-
% @deftypefn {Function File} {[@var{q}, @var{s}] =} qqplot (@var{x}, @var{dist}, @var{params})
% Perform a QQ-plot (quantile plot).
%
% If F is the CDF of the distribution @var{dist} with parameters
% @var{params} and G its inverse, and @var{x} a sample vector of length
% @var{n}, the QQ-plot graphs ordinate @var{s}(@var{i}) = @var{i}-th
% largest element of x versus abscissa @var{q}(@var{i}f) = G((@var{i} -
% 0.5)/@var{n}).
%
% If the sample comes from F except for a transformation of location
% and scale, the pairs will approximately follow a straight line.
%
% The default for @var{dist} is the standard normal distribution.  The
% optional argument @var{params} contains a list of parameters of
% @var{dist}.  For example, for a quantile plot of the uniform
% distribution on [2,4] and @var{x}, use
%
% @example
% qqplot (x, 'uniform', 2, 4)
% @end example
%
% @noindent
% @var{dist} can be any string for which a function @var{dist_inv}
% that calculates the inverse CDF of distribution @var{dist} exists.
%
% If no output arguments are given, the data are plotted directly.
% @end deftypefn

CROSS-REFERENCE INFORMATION ^

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