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NAME

Statistics::Cook - Statistics::Cook - calculate cook distance of Least squares line fit

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 <yanxueqing621@163.com>