[R] Problems with "predict" function ii

[Jeff Newmiller]

This is the kind of thing that leads experienced R users to avoid attach for data analysis. Read "The R Inferno".

Use the "data" argument to lm, and the "newdata" argument to predict.lm.
-- 
Sent from my phone. Please excuse my brevity.

On January 31, 2018 9:20:10 AM PST, WRAY NICHOLAS via R-help <r-help at r-project.org> wrote:
>I  have realised that I should have used "detach" before attaching
>another
>dataframe, but even when I do this it's still giving me lots of lines,
>rather
>than just one:
>
>My code:
>
>
>m<-runif(1,0,1)
>m
>mres<-m*(seq(1,12))
>mres
>ssd<-rexp(1,1)
>ssd
>devs<-rep(0,length(mres))
>for(i in 1:length(mres)){devs[i]<-rnorm(1,0,ssd)}
>devs
>plot(-10,-10,xlim=c(1,24),ylim=c(0,20000))
>sales<-round((mres+devs)*1000)
>
>points(sales,pch=19)
>
>ptr<-cbind(1:length(sales),sales,sales,sales)
>
>ptr
>sdf<-data.frame(cbind(1:nrow(ptr),sales))
>sdf
>
>colnames(sdf)<-c(“monat”,“mitte”)
>sdf
>attach(sdf)
>s.lm<-lm(mitte~monat)
>
>s.lm
>abline(s.lm,lty=2)
>news<-data.frame(monat=nrow(sdf)+1)
>news
>fcs<-predict(s.lm,news,interval=“predict”)
>fcs
>
>points(1+nrow(ptr),fcs[,1],col=“grey”,pch=19)
>points(1+nrow(ptr),fcs[,2])
>points(1+nrow(ptr),fcs[,3])
>ptr<-rbind(ptr,c(1+nrow(ptr),fcs[2],fcs[1],fcs[3]))
>ptr
>
>highdf<-data.frame(ptr[,c(1,4)])
>highdf
>colnames(highdf)<-c(“month”,“sales”)
>highdf
>detach(sdf)
>attach(highdf)
>h.lm<-lm(highdf[,2]~highdf[,1])
>h.lm
>abline(h.lm,col="gray",lty=2)
>news<-data.frame(month=nrow(ptr)+1)
>news
>hcs<-predict(h.lm,news,interval=“predict”)
>hcs
>	[[alternative HTML version deleted]]
>
>______________________________________________
>R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.