Making the plot window wider and using the predict function

Hello,

I am new to R and have a couple of questions. My data set contains the
variables "Bwt" and "Hwt", which are bodyweight and heartweight,
respectively, of a group of cats.
With the following code, I am making two plots, both to be viewed in
the same plot window in R:

library(MASS)
 maleData <- subset(cats, Sex == "M")
 linreg0 <- lm(maleData$Hwt ~ maleData$Bwt)

 par(mfrow=c(1,2))
 plot(maleData$Hwt ~ maleData$Bwt)
 plot(rstandard(linreg0) ~ fitted(linreg0))

My problem is that the two plots end up all oblong and squashed,
because the plot window doesn't have a size suited for having two plots
next to one another. Can I tell R to adjust the plot window?

Also, I would like to do something along the lines of:

newData <- data.frame(Bwt = 3.5)
predict(linreg0,newData,interval="p")

This doesn't work - my guess is that to R, "Bwt" is not a variable in
maleData, but maleData$Bwt is. I could use an attach command, but is it
possible to get this to work without doing so?

Kind regards,
Rasmus Hedegaard.
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