[R] print to .jpeg

[Henrik Bengtsson]

Hi,

First, don't use JPEG for your scientific plots - the image file
format uses a compression that is really bad for anything but photos.
Instead use PNGs. For scientific plots, PNG files are often also
smaller than JPEG files, e.g. in your case the JPEG is ~4 times larger
than the PNG.  See also
http://www.labnol.org/software/tutorials/jpeg-vs-png-image-quality-or-bandwidth/5385/

Next, as already explained, you have to create your own filename
string that you pass to png() (or jpeg() is you still insist on using
that), e.g.

species.name <- "CussoniaHolstii"
filename <- sprintf("%s.png", species.name)
png(filename)
dia <- 10:100
biomass <- -21.4863 + 0.5797 * (dia ^ 2)
plot (biomass, main=species.name, xlab="dbh in cm", ylab="biomass in kg")
dev.off();

Alternatively, use the devEval() function of the R.utils package.
Then the filename extensions is automatically added and the device
automatically closed afterwards, e.g.

library("R.utils");

devEval("png", name=species.name, {
 dia <- 10:100
 biomass <- -21.4863 + 0.5797 * (dia ^ 2)
 plot (biomass, main=species.name, xlab="dbh in cm", ylab="biomass in kg")
})

Use "jpeg" instead of "png" to get a JPEG file, "pdf" to get a PDF and
so on.  Image files are by default written to the figures/ directory
(which is created if missing).  The default directory can be set by
setOption("devEval/args/path", "myImages").

/Henrik


On Tue, Apr 12, 2011 at 7:03 PM, Luke Miller <millerlp at gmail.com> wrote:
> And of course I need to close the parentheses completely on jpeg().
> Apologies for the double post.
>
> jpeg(paste(species.name, '.jpg', sep = ''))
>
> On Tue, Apr 12, 2011 at 10:02 PM, Luke Miller <millerlp at gmail.com> wrote:
>
>> How about using paste() inside the jpeg() function to append a '.jpg' to
>> the end of your species name?
>> See the change below. I also added a dev.off() to close the newly created
>> jpeg.
>>
>>
>> species.name="CussoniaHolstii"
>> dia<-10:100
>> biomass = -21.4863 + 0.5797 * (dia ^ 2)
>> biomass
>> jpeg(paste(species.name, '.jpg', sep = ''))
>>
>> plot (biomass, main=species.name, xlab="dbh in cm", ylab="biomass in kg")
>> dev.off()
>>
>>
>> On Tue, Apr 12, 2011 at 9:54 PM, Benjamin Caldwell <
>> btcaldwell at berkeley.edu> wrote:
>>
>>> Evening folks,
>>>
>>> I'm trying to print a series of graphs to .jpeg using a variable as the
>>> title, but run into the difficultly that I can't find a way to append the
>>> file extension to the .jpeg (in this case extensionless!) files.
>>>
>>> Example:
>>> ----
>>> species.name="CussoniaHolstii"
>>> dia<-10:100
>>> biomass = -21.4863 + 0.5797 * (dia ^ 2)
>>> biomass
>>> jpeg(species.name)
>>> plot (biomass, main=species.name, xlab="dbh in cm", ylab="biomass in kg")
>>> -----
>>> The output is CussoniaHolstii, but I want CussoniaHolstii.jpg. The help
>>> file
>>> for jpeg() specifies that the name include the extension (e.g.
>>> jpeg("CussoniaHolstii.jpg") but then I'd have to input the file name each
>>> time.
>>>
>>> Any help or workaround much appreciated.
>>> *
>>> *
>>> *Ben Caldwell*
>>>
>>>        [[alternative HTML version deleted]]
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide
>>> http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>>
>>
>>
>> --
>> ___________________________
>> Luke Miller
>> Postdoctoral Researcher
>> Marine Science Center
>> Northeastern University
>> Nahant, MA
>> (781) 581-7370 x318
>>
>>
>>
>
>
> --
> ___________________________
> Luke Miller
> Postdoctoral Researcher
> Marine Science Center
> Northeastern University
> Nahant, MA
> (781) 581-7370 x318
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>