Can't print to pdf ggplot charts

Question

Possible Duplicate:
Generate multiple graphics from within an R function

Very strange thing happening to me: the following code fails to print to pdf device:

outnames <- c("1.pdf", "2.pdf")
for (n in outnames){
    pdf(n)
    qplot(1:10)
    dev.off()
}

won't print anything to pdf, even though a pdf file is generated. However,

pdf(outnames[2])
qplot(1:10)
dev.off()

will work perfectly well. Any idea why? Reproduced in R 2.11.1.

score 41 · Accepted Answer · answered Jan 26 '11 at 23:01

41

Gappy, that smells like the FAQ 7.22 -- so please try print(qplot(1:10)).

answered Jan 26 '11 at 23:01

Dirk Eddelbuettel

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Thank you. I'm amazed how counterintuitive R sometimes^Woften is. I must say that the `ggsave` approach below makes more sense to me. – Has QUIT--Anony-Mousse Oct 22 '15 at 14:53

score 12 · Answer 2 · edited Jan 27 '11 at 16:51

12

@Dirk explains why this is happening (auto printing turned off), but an alternative to opening the device, generating the plot on the device, closing the device is ggsave(). For example:

p1 <- qplot(1:10)
ggsave("p1.pdf", plot = p1)

or via a loop:

outnames <- c("1.pdf", "2.pdf")
for (n in outnames){
    p2 <- qplot(1:10)
    ggsave(n, plot = p2)
}

At the end of that we have all the generated plots we asked for.

> list.files(pattern = ".pdf$")
[1] "1.pdf"                  "2.pdf"                 
[3] "p1.pdf"

edited Jan 27 '11 at 16:51

Ken Williams

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answered Jan 27 '11 at 08:04

Gavin Simpson

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Actually his loop works fine, because he's not indexing into `outnames`, he's just using the value. It's the way I would do it too. – Ken Williams Jan 27 '11 at 15:54
Well spotted @Ken that was my own stupidity attached to @Gappy --- will delete the noise! – Gavin Simpson Jan 27 '11 at 16:32
@Ken hmm something seems to be stopping me from accepting your edits. and then I can't edit the post now either... – Gavin Simpson Jan 27 '11 at 16:36
@Shog9 has now approved the edit for me (after posting on meta about the problem). – Gavin Simpson Jan 27 '11 at 16:55
How can you do this but saving all plots to the same file, as `par(mfrow)` does? – Jeni Jun 10 '20 at 12:22

Can't print to pdf ggplot charts

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