Can't display png

Question

I'm running R-shiny (R version 3.0.1 (2013-05-16)) on a VM (Red Hat Enterprise Linux Server release 6.4). Everything works, i.e., server starts up, and application runs etc... as long as I don't try to plot a graph

renderPlot

I then see on the main panel a message [error : unable to start device png]. I would post my whole code but this problem I think has to do with rendering plots as when I use renderText and spit out some data it works just fine.

Actually when I just type in png() in R I get this error [ Error in .External2(C_X11, paste("png::", filename, sep = ""), g$width, : unable to start device PNG In addition: Warning message: In png() : unable to open connection to X11 display '' ] of course if I forward via ssh -X to my mac, I can type in png() no problem and plot data etc...

-A few more things to note, when I type in capabilties() I find the only things that are false are jpeg, tiff, X11, aqua, and profmem (so png and cairo are True)

-I've installed libpng, cairo, and libX11, libX11-devel, libXt, libXt-devel before building R from source

I'm guessing my problem is that I need to have X server running. In addition the DISPLAY variable is null.

So, I guess when it boils down to it my question is ... assuming my logic is correct.

1) Do I need to run / start X server [ currently it terminates after starting for some reason] or can I just set the DISPLAY variable?

2) If I can just set my DISPLAY variable what should I set it to (localhost:0.0 hasn't worked)

Obviously if there is something I'm missing these questions may be irrelevant.

Thanks in advance and sorry for rambling, wanted to be thorough.

PJ

Speculator

The DISPLAY variable should point to a working X server, otherwise there's very little sense in setting it. – Mattah

May point you in the right direction: trestletechnology.net/2013/02/… – Dottiedottle

Answer 1

Does it help if you set option(bitmapType = 'cairo')? I have been skeptical about how R chooses the bitmap device type using .Call(C_cairoProps, 2L) in grDevices:::.onLoad() (this might be a bug, but I cannot say it for sure).

The option bitmapType falls back to Xlib if the test of cairo fails, thus giving you a cryptic error message about X11. Note the type argument in png():

> args(png)
function (filename = "Rplot%03d.png", width = 480, height = 480, 
    units = "px", pointsize = 12, bg = "white", res = NA, ..., 
    type = c("cairo", "cairo-png", "Xlib", "quartz"), antialias) 

The default value of this argument is getOption('bitmapType'), and in your case it is Xlib due to the test in grDevices:::.onLoad(). If you are 100% sure that cairo works, you can change this option, say, in your ~/.Rprofile.

Vandalism

Hello Yihui. Do you suggest to set option(bitmapType='cairo') in the server.R file ? – Verlie

@StéphaneLaurent yes, that is also one way to go; I mentioned ~/.Rprofile above, which means to set this option globally for all your R sessions – Vandalism

I have tried options(bitmapType='cairo') in the server.R file but that does not change anything. – Verlie

@StéphaneLaurent you mean exactly the same error message? can you simply test png(tempfile(), type='cairo'); dev.off()? – Vandalism

Yes exactly the same error message. Do you mean typing this line as a command line ? (I'll try tomorrow, I'm at home now) – Verlie

@StéphaneLaurent Yes, type the code as a command line in an R terminal. The same error message indicates the option was not respected, so I ask you to hardcode the option and see if it works. – Vandalism

Yihu, my colleague (Linux server admin) has recompiled R-3.0.1 with cairo, and now everything works well with options(bitmapType='cairo') ! Thank you ! – Verlie

I had to add options(bitmapType='cairo') to my ~/.Rprofile – Chemisette

Answer 2

I was able to resolve this by installing a few additional development packages and then uninstalling/reinstalling R from source. All the other recommended options did not work for me until this.

sudo yum install pango-devel pango libpng-devel

Go to directory where source R file was installed:

make uninstall
./configure --with-readline=no (or ./configure might work for you)
make
make install

Smutty