[R] Issues getting R to write image files

[(Ted Harding)]

On 11-Jun-09 09:24:42, Tobias Verbeke wrote:
> Hi Kenny,
> 
>> Have spent the last couple of days learning R and shell scripting to
>> do
>> batch plotting jobs. I have had success getting R to complete a filled
>> contour plot and output to a file (.jpg or .tiff etc). However, when I
>> try
>> to do the same thing with the simple plot command the script seems to
>> execute correctly yet there is no output. Below is my R code: 
>> 
>> file <- Sys.getenv("input_file") 
>> tiff(paste( file, "tiff", sep="."))
>> z <- read.table(file) 
>> plot(z, type="l", xlim=range(0.6,2), col = "red", plot.title =
>> title(main =
>> file, xlab = "Wavelength (um)", ylab = "Intensity (arb.)) 
> 
> dev.off()
> 
>> q() 
> 
> You need to close the tiff graphics device you opened
> using dev.off() before quitting.
> 
> HTH,
> Tobias

I thought of that too -- since the graphics device needs to be
closed before writing out to the file is completed and the file
is closed.

However, it occurred to me that possibly q() would also have that
effect, since it closes down R which should have the effect of
closing devices, flushing buffers, and closing files (though I do
not see this documented under "?q").

So I experimented.

1. New R session.
2. Assign values to some variables.
3. Open a tiff() device, plot them, and quit R (no dev.off):

  tiff(file="temp.tif")
  plot (X,P,  type="l")
  lines(X,I.b,         col="blue" )
  lines(X,I.m,         col="green")
  lines(X,I.bm^2,      col="red")
  q()

4. End of R session, and temp.tif (which did not exist at the start)
contains a good TIFF file with exactly what I expected to see. This
confirmed my suspicions.

So it sould seem that dev.off() is not the answer.

Probably something is wrong along the line of reading in the data,
or in specifying what to plot. But I can't see anything obvious in
the code, so it may depend on what sort of structure z is, for instance.

Ted.


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Date: 11-Jun-09                                       Time: 10:43:51
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