twintotalchi: Total Scaled Chi-square of All Divisions and Groups

In jarioksa/twinspan: Two-Way Indicator Species Analysis

Total Scaled Chi-square of All Divisions and Groups

Description

Total scaled Chi-square is the same as the sum of all eigenvalues in Correspondence Analysis. It is a measure of heterogeneity of a set of data. The function finds this measure for all divisions and terminal groups in twinspan

Usage

totalchi(x)

twintotalchi(x, what = c("quadrat", "species"))

Arguments

x	A matrix of non-negative data for totalchi or a twinspan result object for twintotalchi.
what	Analyse quadrat or species classification.

Details

Function first reconstructs the data as it was internally used in twinspan using functions twin2stack and twin2specstack. The scaled Chi-square is calculated with support function totalchi that can be called independently for any matrix with non-negative data. The scaling in Chi-square means that data are standardized to unit sum before calculating the actual Chi-square. This is often called the sum of all eigenvalues in Correspondence Analysis, but no eigenvalues are evaluated in these functions, only their potential sum.

See Also

The basic functions are twin2stack and twin2specstack that construct the data matrices.

Examples

data(ahti)
tw <- twinspan(ahti)
twintotalchi(tw)

jarioksa/twinspan documentation built on Nov. 23, 2024, 2:49 p.m.