RVAideMemoire (version 0.9-45-2)

back.lsmeans: Back-transformation of LSMeans

Description

Back-transforms LSMeans (produced by lsmeans) when the model was built on a transformed response variable. This is typically the case when a LM(M) with log(x+1) as response variable gives a better fitting than a GLM(M) for count data.

Usage

back.lsmeans(lsm, transform = c("log", "logit", "sqrt", "inverse"), base = exp(1),
  add=0)

Arguments

lsm

object returned by lsmeans.

transform

transformation applied to the response variable before building the model on which lsm is based.

base

the base with respect to which the logarithm transformation was computed (if transform="log"). Defaults to e=exp(1).

add

value added to x before computing the transformation, if needed (e.g. 1 if the initial transformation was log(x+1)).

See Also

lsmeans

Examples

require(lsmeans)

set.seed(1149)
response <- c(rpois(30,0),rpois(30,2),rpois(30,4))
fact <- gl(3,30,labels=LETTERS[1:3])

model <- lm(log(response+1)~fact)
LSM <- lsmeans(model,~fact)
back.lsmeans(LSM,transform="log",add=1)