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Problems with "predict" function ii

4 messages · WRAY NICHOLAS, Jeff Newmiller, PIKAL Petr +1 more

Original
WRAY NICHOLAS
# 
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
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.
PIKAL Petr
# 
Hi

First of all you should not post in HTML.

Thank you for posting the code, however I do not understand wht exactly do you mean by that you get many lines. I get only one with your code.

Other answers see in line

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of WRAY NICHOLAS via R-help
Sent: Wednesday, January 31, 2018 6:20 PM
To: r-help <r-help at r-project.org>
Subject: [R] Problems with "predict" function ii

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:



And you should not use attach, it is hardly ever necessary.

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)


instead of attach use
s.lm<-lm(mitte~monat, data=sdf)


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<-lm(sales~month, highdf)


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

I get a picture with two lines, black from you first call to the abline, second from your second call. What you want to achieve?

Cheers
Petr




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Rui Barradas
# 
Hello,

First of all, your question is about 'predict' but you include graphic 
instructions that have nothing to do with it. They do not hurt, but the 
reproducible example should also be minimal.

Second, whenever you use RNG's, you should start it with set.seed().

Now, I have edited your code and it all works. No errors.
I got it rid of attach/detach and of the graphics.
And added spaces around some bits, such as <-, =, etc.


set.seed(187)    # Make the results reproducible

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
sales <- round((mres+devs)*1000)

ptr <- cbind(1:length(sales), sales, sales, sales)
ptr

sdf <- data.frame(1:nrow(ptr), sales)
colnames(sdf)<-c("monat", "mitte")
sdf

#attach(sdf)
s.lm <- lm(mitte ~ monat, sdf)
s.lm

news <- data.frame(monat = nrow(sdf) + 1)
news

fcs <- predict(s.lm, newdata = news, interval = "predict")
fcs

ptr <- rbind(ptr, c(1 + nrow(ptr), fcs[2], fcs[1], fcs[3]))
ptr

highdf <- data.frame(ptr[, c(1, 4)])
colnames(highdf) <- c("month","sales")
highdf

#detach(sdf)
#attach(highdf)
h.lm <- lm(sales ~ month, highdf)
h.lm
news <- data.frame(month = nrow(ptr) + 1)
news
hcs <- predict(h.lm, newdata = news, interval = "predict")
hcs
On 1/31/2018 5:20 PM, WRAY NICHOLAS via R-help wrote: