# NAME Statistics::Cook - Statistics::Cook - calculate cook distance of Least squares line fit # VERSION version 0.0.6 # SYNOPSIS use Statistics::Cook; my @x = qw/1 2 3 4 5 6/; my @y = qw/1 2.1 3.2 4 7 6/; my $sc = Statistics::Cook->new(x => \@x, y => \@y); ($intercept, $slope) = $sc->coefficients; my @predictedYs = $sc->fitted; my @residuals = $sc->residuals; my @cooks = $sc->cooks_distance; # DESCRIPTION The Statistics::Cook module is used to calculate cook distance of Least squares line fit to two-dimensional data (y = a + b \* x). (This is also called linear regression.) In addition to the slope and y-intercept, the module, the predicted y values and the residuals of the y values. (See the METHODS section for a description of these statistics.) The module accepts input data in separate x and y arrays. The optional weights are input in a separate array The module is state-oriented and caches its results. you can call the other methods in any order or call a method several times without invoking redundant calculations. # LIMITATIONS The purpose of I write this module is that I could not find a module to calculate cook distance in CPAN, Therefore I just realized this module with a minimized function consists of least squares and cook distance # ATTRIBUTES ## x x coordinate that used to linear regression and cook distance, is a ArrayRef ## y y coordinate that used to linear regression and cook distance, is a ArrayRef ## weight weights that used to linear regression and cook distance, is a ArrayRef ## slope slope value of linear model ## intercept intercept of y in linear model ## regress\_done the status whether has done linear regress # METHODS The module is state-oriented and caches its results. Once you have done regress, you can call the other methods in any order or call a method several times without invoking redundant calculations. The regression fails if the x values are all the same. In this case, the module issues an error message ## regress Do the least squares line fit, but you don't need to call this method because it is invoked by the other methods as needed, you can call regress() at any time to get the status of the regression for the current data. ## computeSums Computing some value that used by regress, that you usually need not use it. ## coefficients Return the slope and y intercept ## fitted Return the fitted y values ## residuals Return residuals of y values ## cooks\_distance Calculate cook distance of linear model ## N default is get N50 of a ArrayRef $self->N(\[1,2,3,4\], 90), you will get N90 $self->N(\[1,2,3,4\], 80), you will get N80 ## mean mean value of an array ## var The variance of a set of samples ## sd The standard deviation of a set of samples # AUTHOR Yan Xueqing # COPYRIGHT AND LICENSE This software is copyright (c) 2015 by Yan Xueqing. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.