On Mar 10, 2011, at 05:49 , Tyler Rinker wrote:
>
> My Question: What do I need to do to correct the three error codes R gives
> me and make the function run correctly?
>
> This is the session, code and R's error message when supplied with data:
>> rm(list=ls())
>> dat1<-read.table("dat1.csv", header=TRUE, sep=",",na.strings="999")
>> attach(dat1)
>> dat1
> student rti score
> 1 1 ns 2
> 2 2 ns 5
> 3 3 ns 2
> 4 4 ns 11
> 5 5 wk2o 10
> 6 6 wk2o 11
> 7 7 wk2o 7
> 8 8 wk2o 12
> 9 9 wk5o 12
> 10 10 wk5o 12
> 11 11 wk2w 5
> 12 12 wk2w 6
> 13 13 wk2w 12
> 14 14 wk5w 5
> 15 15 wk5w 6
> 16 16 wk5w 13
>> anova(lm(score~rti))
> Analysis of Variance Table
> Response: score
> Df Sum Sq Mean Sq F value Pr(>F)
> rti 4 83.771 20.943 1.7107 0.2174
> Residuals 11 134.667 12.242
>> #so MSw is 12.242
>>
>> #my code for scheffe's post hoc comparison
>>
>> scheffe<- function(IV,DV,data,group1,group2,MSw,alpha) {
> + result<-0
> + J<-length(levels(IV))
> + d1<-subset(data, IV == "group1")
> + d2<-subset(data, IV == "group2")
> + g1<-d1$DV
> + g2<-d2$DV
This is your problem. You seem to think that d1$DV extracts d1$score when score
is passed in the DV argument, but it goes looking for a DV component. For a
quick fix, pass "score" as a character string and use d1[[DV]]. Also beware
that your IV argument is passed by value, so it may not be available, and if
available, it may not be the object that you are looking for.
> + y.1<-mean(g1)
> + y.2<-mean(g2)
> + n1<- length(g1)
> + n2<- length(g2)
> + N<-length(IV)
> + psi.hat<-y.1-y.2
> + se.psi.hat<- sqrt(MSw*((1/n1)+(1/n2)))
> + t<- psi.hat/se.psi.hat
> + t.compare<-abs(t)
> + k<-sqrt((J-1)*( qf((1-alpha),(J-1),(N-J))))
> + if(t.compare > k) return<-c("reject H0") else result<- c("accept H0")
> + return(list(cbind(result)), Mean.Group.1 = y.1,n.for.1=n1,
> + Mean.Group.2=y.2,n.for.2=n2,N.Data=N,tValue=t,critical.value=k)
> + }
>> #
>> #doesn't seem to be a problem thus far
>> #let's enter some data
>>
>> #scheffe(IV,DV,data,group1,group2,MSw,alpha)
>>
>> scheffe(rti,score,dat1,ns,wk5o,12.242,.05)
> Error in if (t.compare > k) return <- c("reject H0") else result <- c("accept
> H0") :
> missing value where TRUE/FALSE needed
> In addition: Warning messages:
> 1: In mean.default(g1) : argument is not numeric or logical: returning NA
> 2: In mean.default(g2) : argument is not numeric or logical: returning NA
>>
>
>
> [[alternative HTML version deleted]]
>
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--
Peter Dalgaard
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd....@cbs.dk Priv: pda...@gmail.com
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