pgirmess (version 1.3.8)

PermTest: Permutation test for lm, lme and glm (binomial and Poisson) objects

Description

Permutation test for lm, lme and glm (binomial and Poisson) objects

Usage

PermTest(obj, B=1000,...)

    ## S3 method for class 'lm':
PermTest(obj, B=1000,...)
    ## S3 method for class 'lme':
PermTest(obj, B=1000,...)
    ## S3 method for class 'glm':
PermTest(obj, B=1000,...)

Arguments

obj

an object of class lm, lme, or glm

B

number of permutations, default = 1000

...

used to pass other arguments

Value

• A list object of class PermTest including:
• p.value
  the p value obtained
• B
  the number of permutations
• call
  the call

Warning

This generic function is implemented in R language, thus can be quite slow.

Details

For glm, when the response is a two-column matrix with the columns giving the numbers of successes and failures, PermTest.glm uses permcont(); PermTest.lme requires the library nlme.

Examples

library(MASS)
mylm<-lm(Postwt~Prewt,data=anorexia)
PermTest(mylm,B=250)

## Dobson (1990) Page 93: Randomized Controlled Trial :
    counts <- c(18,17,15,20,10,20,25,13,12)
    outcome <- gl(3,1,9)
    treatment <- gl(3,3)
    glm.D93 <- glm(counts ~ outcome + treatment, family=poisson)
    PermTest(glm.D93,B=250)

library(nlme)
fm2 <- lme(distance ~ age + Sex, data = Orthodont, random = ~ 1)
PermTest(fm2,B=250)