Rserve graphics output [was Re: C or Java code generation]
On Fri, 2010-08-20 at 12:58 -0400, Sharpie wrote:
Donald Paul Winston wrote:
Aren't you the guy who created Rserve? I'd like to develop a web app so clients can perform exploratory data analysis with their browser with no installed software, not even java (I don't like applets). I thought R would be excellent for this but I need some issues cleared up before I invest a lot of time working with it.
Well, Simon is the one who create Rserve. However, if you have questions about Rserve it may be best to start a new thread or at least change the subject header of your message. This discussion was about creating stand-alone executables that use R code for deployment on a desktop. Donald Paul Winston wrote:
It appears R insists on directing plot output to a file. Is their a graphics device that keeps the output in memory so it can be returned to my java app as a stream of bytes? If I have to wait for it to write to a "unique file" and then read it back again then I don't think that's going to work. My web app needs to support hundreds of concurrent clients.
As far as I know all R graphics output that does not go to a screen device, such as an X window, must be directed to some sort of file. I am not aware of a graphics device that provides output to something other than a screen or a file, but there very well may be such a device in existence.
This was essentially the conclusion of Donald's earlier thread...
The functionality you could describe could be implemented by writing a R graphics device that forwards the R plotting commands to... well anywhere you want, really. As the author of an R graphics device, I can say the trickiest part of such an undertaking will be calculating font metrics so that R can properly position text in the graphics. Everything else is very straight-forward.
I believe Donald wants the _rendered_ output. That is, a stream of bytes that represent a png, jpeg, etc. Toward this end, we have already discussed using an OS-level fifo to avoid disk I/O, and I think this is the easiest route for Donald. Alternatively, Donald might look into the X11 graphics driver, where Cairo is used to write pngs. In particular, the in_do_saveplot function (src/main/modules/X11/devX11.c) calls cairo_surface_write_to_png, in order to save a png to file. Cairo also provides the cairo_surface_write_to_png_stream function, which might be used to send png data to a memory buffer (i.e. a raw vector). I don't think it would be too difficult to modify in_do_saveplot to accommodate this.
I have plans to write a device that forwards the plotting commands to a socket connection that allows another program to execute them. In my case, an Erlang backbone is used to route the results back to web clients using websockets. The idea is to have the plot rendered directly in the client's browser using a JavaScript library like RaphealJS. However, the school year is upon me and the project will probably remain on the drawing board until next summer. Donald Paul Winston wrote:
Is REngine.jar and REngineRserve.jar all I need in my web app?
I can't comment on REngine as I have not used it. Donald Paul Winston wrote:
Also, how come their is no shutdown command from the command line for Rserve. I see one in the java client api. Do I have to write my own?
I find that on UNIX a SIGTERM, SIGSTOP or SIGKILL signal broadcast using a command line utility such as kill does the job. -Charlie ----- Charlie Sharpsteen Undergraduate-- Environmental Resources Engineering Humboldt State University
Matthew S. Shotwell Graduate Student Division of Biostatistics and Epidemiology Medical University of South Carolina