Suppressing "null device" output with R in batch mode

r bash plot suppress-warnings
blahdiblah picture blahdiblah · Apr 15, 2009 · Viewed 19.9k times · Source

I have a number of bash scripts which invoke R scripts for plotting things. Something like: 

#!/bin/bash
R --vanilla --slave <<RSCRIPT
cat("Plotting $1 to $2\n")
input <- read.table("$1")
png("$2")
plot(as.numeric(input[1,]))
dev.off()
RSCRIPT

The problem is that despite --slave, the call to dev.off() prints the message null device 1. Once there are a lot of plots being done, or for more complex scripts which plot to a number of files, this gets to be a real hassle.

Is there some way to suppress this message?

Answer

blahdiblah picture blahdiblah · Apr 15, 2009

For no good reason I'm aware of, dev.off(), unlike device related functions like png() returns a value: "the number and name of the new active device." That value is what's being echoed to stdout.

Suppressing it can thus be achieved by just putting it somewhere, i.e.,

garbage <- dev.off()

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