disco {energy} R Documentation

distance components (DISCO)

Description

E-statistics DIStance COmponents and tests, analogous to variance components and anova.

Usage

disco(x, factors, distance, index=1.0, R, method=c("disco","discoB","discoF"))
disco.between(x, factors, distance, index=1.0, R)


Arguments

 x data matrix or distance matrix or dist object factors matrix of factor labels or integers (not design matrix) distance logical, TRUE if x is distance matrix index exponent on Euclidean distance in (0,2] R number of replicates for a permutation test method test statistic

Details

disco calculates the distance components decomposition of total dispersion and if R > 0 tests for significance using the test statistic disco "F" ratio (default method="disco"), or using the between component statistic (method="discoB"), each implemented by permutation test.

If x is a dist object, argument distance is ignored. If x is a distance matrix, set distance=TRUE.

In the current release disco computes the decomposition for one-way models only.

Value

When method="discoF", disco returns a list similar to the return value from anova.lm, and the print.disco method is provided to format the output into a similar table. Details:

disco returns a class disco object, which is a list containing

 call call method method statistic vector of observed statistics p.value vector of p-values k number of factors N number of observations between between-sample distance components withins one-way within-sample distance components within within-sample distance component total total dispersion Df.trt degrees of freedom for treatments Df.e degrees of freedom for error index index (exponent on distance) factor.names factor names factor.levels factor levels sample.sizes sample sizes stats matrix containing decomposition

When method="discoB", disco passes the arguments to disco.between, which returns a class htest object.

disco.between returns a class htest object, where the test statistic is the between-sample statistic (proportional to the numerator of the F ratio of the disco test.

Note

The current version does all calculations via matrix arithmetic and boot function. Support for more general additive models and a formula interface is under development.

disco methods have been added to the cluster distance summary function edist, and energy tests for equality of distribution (see eqdist.etest).

Author(s)

Maria L. Rizzo mrizzo@bgsu.edu and Gabor J. Szekely

References

M. L. Rizzo and G. J. Szekely (2010). DISCO Analysis: A Nonparametric Extension of Analysis of Variance, Annals of Applied Statistics, Vol. 4, No. 2, 1034-1055.
doi: 10.1214/09-AOAS245

 edist   eqdist.e   eqdist.etest   ksample.e

Examples

      ## warpbreaks one-way decompositions
data(warpbreaks)
attach(warpbreaks)
disco(breaks, factors=wool, R=99)

## When index=2 for univariate data, we get ANOVA decomposition
disco(breaks, factors=tension, index=2.0, R=99)
aov(breaks ~ tension)

## Multivariate response
## Example on producing plastic film from Krzanowski (1998, p. 381)
tear <- c(6.5, 6.2, 5.8, 6.5, 6.5, 6.9, 7.2, 6.9, 6.1, 6.3,
6.7, 6.6, 7.2, 7.1, 6.8, 7.1, 7.0, 7.2, 7.5, 7.6)
gloss <- c(9.5, 9.9, 9.6, 9.6, 9.2, 9.1, 10.0, 9.9, 9.5, 9.4,
9.1, 9.3, 8.3, 8.4, 8.5, 9.2, 8.8, 9.7, 10.1, 9.2)
opacity <- c(4.4, 6.4, 3.0, 4.1, 0.8, 5.7, 2.0, 3.9, 1.9, 5.7,
2.8, 4.1, 3.8, 1.6, 3.4, 8.4, 5.2, 6.9, 2.7, 1.9)
Y <- cbind(tear, gloss, opacity)
rate <- factor(gl(2,10), labels=c("Low", "High"))

## test for equal distributions by rate
disco(Y, factors=rate, R=99)
disco(Y, factors=rate, R=99, method="discoB")

## Just extract the decomposition table
disco(Y, factors=rate, R=0)\$stats

## Compare eqdist.e methods for rate
## disco between stat is half of original when sample sizes equal
eqdist.e(Y, sizes=c(10, 10), method="original")
eqdist.e(Y, sizes=c(10, 10), method="discoB")

## The between-sample distance component
disco.between(Y, factors=rate, R=0)


[Package energy version 1.7-10 Index]