Hello, I'd like to know how to plot the residual into a graphics in real-time during the running of my own code. It's a code written in C, compiled with gcc and run as an executable, and the only way I have now to view the diagram of the residual is printing out the values and only afterwards to view them through octave/gnuplot or matlab.

Anyone worte a script to let the executable communicate with a visualization tool?

Thanks a lot

Simone

You could use pgplot.

http://www.astro.caltech.edu/~tjp/pgplot/

I use a much simpler solution. From my code I run gnuplot (use the system subroutine which is available in both fortran and C) to generate a png file of the residue plot. I open the png file with xv or display (part of imagemagick); the image display gets updated automatically whenever the png file is modified.

Thank you very much for the hint. Ill work on it starting from your suggestion. In case I want to use your way, calling gnuplot from C, would it be called as: system(gnuplot 'filename') ?

thanks again

simone

Found this some time ago:


c Fortran-gnuplot interaction for real-time animation using named pipe
c
c This is a simple example of how gnuplot can be used to create
c real-time animation of data produced by running fortran 77 code.
c
c I put it in the searchable directory in a hope that it can be useful,
c but no guarantees of any kind: use it at your own risk. Too many
c frames per second can hang you system heavily.
c
c To understand how it works, you need to know what a named pipe is, and what
c plot '-' means in gnuplot: read the manuals.
c
c And, PLEASE, if you know why a.out > FIFOfile works
c but just a.out does not
c even though the gnuplot commands are written to the pipe and not
c to the standard output, send me an explanation to
c chernysh@soton.ac.uk (Sergei Chernyshenko) or
c by other means, see http://www.afm.ses.soton.ac.uk/ -> People.
c
c How to use:
c
c at the linux command prompt, type mkfifo FIFOfile
c compile this file and name the executable a.out .
c in an xterm window type gnuplot < FIFOfile
c in another window type a.out > FIFOfile
c enjoy
c
c do not use too many frames per second, the computer may hang.
c
c second(x) gives the CPU time in seconds. Replace if unavailable.

nframe=0
open(1,file='FIFOfile', status='unknown')
write(1,*) 'set xrange [-10:10]'
write(1,*) 'set yrange [-2:2]'
write(1,*)'set title \'Demonstrating animation Fortran-gnuplot'
1 ,' via named pipe\''
close(1)
1 call second(x)
c 15 frames per second:
if(15*x.gt.nframe) then
nframe=nframe+1
open(1,file='FIFOfile', status='unknown')
write(1,*) 'plot sin(x-',x,'),',' \'-\' w lp'
write(1,*) 0.2
write(1,*) 0.3
write(1,*) 0.4
write(1,*) 0.5
i=(x/10)
i=i*10
write(1,*) (x-i)/10.
write(1,*) 0.7
write(1,*) 0.8
write(1,*) 0.9
write(1,*) 'e'
close(1)
endif
goto 1
stop
end

Very useful, thanks

s.

Say you have put all your gnuplot commands in file "plot.gnu". In C you would run gnuplot as

system("gnuplot plot.gnu");

Suppose gnuplot generates plot.png

You open it in xv as

xv -poll plot.png &

or in display as

display -update 10 plot.png &

You can also start the image viewer from within your C code.

I try this and let you know. Supposedly then this same thing would work also if I generate my plots with octave? For exemple I could view a vector field step by step during the exsecution of my C code?

system("octave plot.gnu");