On Sep 19, 2009, at 5:37 AM, Sam Player 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$f==i, 2]
jpeg(filename=(levels(df[i,"f"])))
hist(y, main=levels(df[i,"f"]))
dev.off()
}
You are a bit unclear about what you are seeking but if you want
separate file names and titles that are factor-specifich, then why not
use "i" inside the loop as itself?
for (i in levels(df[,"f"])){
y <- df[df$f==i, 2]
jpeg(filename=paste("file_",i,sep=""))
hist(y, main=paste("Factor =",i,sep=""))
dev.off()
}
# I'm obviously not understanding how loops work with factors.
It seems that you are unclear about loop indices. You are not really
passing factors anyway, but rather elements of a character vector,
levels(df[,"f"]).
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: spla...@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
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
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