You could plot both histograms into the same file using this:
library(lattice)
jpeg(filename="combined.jpeg")
histogram(~d|f, data = df)
dev.off()

Schalk Heunis


On Sat, Sep 19, 2009 at 11:37 AM, Sam Player <samtplayer@gmail.com> wrote:

> # I have a dataframe with data and factors similar to the following:
>
> a <- rep(c("a", "b"), c(6,6))
> df <- data.frame(f=a, d=rnorm(12))
> df
>
> # I am trying to write a 'for' loop which will produce a jpeg histogram for
> each factor. I can individually isolate the data from a factor and produce a
> jpeg histogram like so:
>
> fnc <- function(x){
>        x <- df[df$f=="a", "d"]
> }
>
> y <- fnc(df[df$f=="a", "d"])
>
> jpeg(filename="foo.jpeg")
> hist(y)
> dev.off()
>
> # I'm having trouble creating a loop repeating the process for all the
> other factors. The following is the best I could come up with. It produces a
> single jpeg histogram of the first factor titled with a list of all the
> factors.
>
> a <- rep(c("a", "b"), c(6,6))
> df <- data.frame(f=a, d=rnorm(12))
> df
>
> for (i in levels(df[,"f"])){
>        y <- df[df$f==i, 2]
>        jpeg(filename=(levels(df[i,"f"])))
>        hist(y, main=levels(df[i,"f"]))
>        dev.off()
>        }
>
> # I'm obviously not understanding how loops work with factors. Can anybody
> point me in the right direction?
>
> --
> Sam Player, B.Sc.(Hons.) B.A.
> Ph.D. Candidate, Faculty of Agriculture, Food & Natural Resources,
> University of Sydney
>
> Email: splayer@usyd.edu.au
>
> Agroecosystems Research Group
> Room 214 J.R.A. McMillan Building A05
> University of Sydney NSW 2006, Australia
>
> Angkor Research Program
> Room 305 Old Teachers College A22
> University of Sydney NSW 2006, Australia
>
> ______________________________________________
> R-help@r-project.org mailing list
> 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.
>

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