subsetting a dataframe
On 3/4/2008 8:41 AM, John Sorkin wrote:
windows XP R 2.6.0 I am having problems deleting a row from a data frame. I create my dataframe by subsetting a larger dataframe: ShortLavin<-Lavin[Lavin[,"Site"]=="PP" | Lavin[,"Site"]=="CC" | Lavin[,"Site"]=="FH",]
I would do that in the following way:
ShortLavin <- subset(Lavin, Site %in% c("PP","CC","FH"))
I then perform a glm using the data frame and plot the results. fit1poisson<-glm(NumUniqOpPt~Seq+Site,family=poisson(link = "log"),data=ShortLavin,offset=log(NumUniqPt)) plot(fit1poisson)
Of course, you could have done the subsetting within the call to glm:
fit1poisson <- glm(NumUniqOpPt~Seq+Site,family=poisson(link = "log"),
data=subset(Lavin, Site %in% c("PP","CC","FH")),
offset=log(NumUniqPt))
On the plots I see a point labeled as 127 that is an extreme value. I want to re-run the glm excluding the extreme observation. I have tried several methods to exclude the observation (shown below), none have worked.
Minus127<-ShortLavin[-127,]
Minus127<-ShortLavin[-"127",]
Minus127<-ShortLavin[-c(127),]
Minus127<-ShortLavin[-c("127"),]
None of these worked. Suggestions on how I can remove observation 127 would be appreciated
Minus127 <- subset(ShortLavin, !rownames(ShortLavin) %in% 127)
Thank you,
John
John Sorkin M.D., Ph.D.
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology
Baltimore VA Medical Center
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