R help - Apr 2010 - pdf files in loops

I need to make a bunch of PDF files of histograms. I tried
gatelist = unique(mdf$ArrivalGate)
for( gate in gatelist) {       
    outfile = paste("../", airport, "/", airport,
"taxiHistogram", gate,
".pdf", sep="")
    pdf(file = outfile, width = 10, height=8, par(lwd=1))

    title=paste("Taxi time for Arrival Gate", gate, "by Runway
at", airport)
    gdf = mdf[mdf$ArrivalGate == gate, ]
    gdf$tt= gdf$TaxiTime/60           
    histogram(~(gdf$tt) | gdf$Runway, data=gdf, type="count",
ylab="Count",    breaks=20, main=title,
                        xlab="taxi time (min)",  
par.strip.text=list(cex=0.7))
    dev.off()
}

But when I do this, the pdf files are all empty. If I eliminate the call
to pdf() and dev.off(), and step through the loop manually, the
histograms still do not plot, even though any one of them will plot.

What am I doing wrong?

Thanks,
Jim Rome

G'day James,

On Wed, 31 Mar 2010 21:44:31 -0400
James Rome <jamesrome at gmail.com> wrote:
> I need to make a bunch of PDF files of histograms. 
[...]
> What am I doing wrong?
http://cran.ms.unimelb.edu.au/doc/FAQ/R-FAQ.html#Why-do-lattice_002ftrellis-graphics-not-work_003f

HTH.

Cheers,

	Berwin

========================== Full address ===========================Berwin A
Turlach                      Tel.: +61 (8) 6488 3338 (secr)
School of Maths and Stats (M019)            +61 (8) 6488 3383 (self)
The University of Western Australia   FAX : +61 (8) 6488 1028
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Crawley WA 6009                e-mail: berwin at maths.uwa.edu.au
Australia                        http://www.maths.uwa.edu.au/~berwin

Have you tried
plot(pic)

-----Original Message-----
From: Berwin A Turlach <berwin at maths.uwa.edu.au>
Sent: Wednesday, March 31, 2010 10:15 PM
To: James Rome <jamesrome at gmail.com>
Cc: r-help at r-project.org <r-help at r-project.org>
Subject: Re: [R] pdf files in loops

On Wed, 31 Mar 2010 22:06:48 -0400
James Rome <jamesrome at gmail.com> wrote:
> print() did not help, and I get strange messages about mode(onefile)
> not being changed:
Either:

R> pic <- histogram(...)
R> print(pic)

or

R> print(histogram(...))
> I would actually like all the histograms in one pdf file too...
Then move the pdf() and the dev.off() commands outside the loop.

HTH.

Cheers,

	Berwin

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