[R] Tukey "no factors"

[arun]

HI,
May be the below links help:
http://r.789695.n4.nabble.com/TukeyHSD-troubles-td1570205.html
http://r.789695.n4.nabble.com/TukeyHSD-error-td3051059.html


A.K.



Hi

I'm trying to run a Tukey test on mortality data, where I want to test whether mortality is influenced by the amount of copper (in an one-way ANOVA) and the combination of copper and temperature (in a two-way ANOVA). These are my formulas:

lm2<-lm(Mortality~Cu)
anova(lm2)
TukeyHSD(aov(Mortality~Cu))

lm2<-lm(Mortality~Cu+Temp+Cu:Temp)
anova(lm2)
TukeyHSD(aov(Mortality~Cu+Temp+Cu:Temp))

The ANOVA is no problem, but for both Tukey's, I get the following error message:

Error in TukeyHSD.aov(aov(Mortality ~ Cu + Temp + Cu:Temp)) :
  no factors in the fitted model
In addition: Warning messages:
1: In replications(paste("~", xx), data = mf) : non-factors ignored: Cu
2: In replications(paste("~", xx), data = mf) : non-factors ignored: Temp
3: In replications(paste("~", xx), data = mf) :
  non-factors ignored: Cu, Temp

I've read on other posts that there should be a factor somewhere, but all my data are numbers! I'm quite baffled and have no idea what to do next.

Thanks in advance for your help!

Lundill