How to plot data by c program?

Question

I am a mechanical engineer who has only limited knowledge in C programming. I wrote some code in order to make simulations, and I want to visualize the simulation results. A

Answer 1

I've been using PLPlot for plotting from C and have found it both effective and easy. It's cross platform, open source, and supports a rich array of plot capabilities. I'd recommend having a look at the examples to get started.

Answer 2

pbPlots is very easy to use and works with all C compilers.

Download pbPlots.c/h and supportLib.c/h from the github page and include them in your build.

Here is a complete example that will produce a plot in a PNG-file.

#include "pbPlots.h"
#include "supportLib.h"

int main(){

    double x [] = {-1, 0, 1, 2, 3, 4, 5, 6};
    double y [] = {-5, -4, -3, -2, 1, 0, 1, 2};

    RGBABitmapImageReference *imageRef = CreateRGBABitmapImageReference();

    DrawScatterPlot(imageRef, 600, 400, x, 8, y, 8);

    size_t length;
    double *pngData = ConvertToPNG(&length, imageRef->image);
    WriteToFile(pngData, length, "plot.png");

    return 0;
 }

There are a lot more options available, these are described on the github page.

Answer 3

I had a wee look around to see what other people have done regarding real-time plotting in gnuplot, and found this:

http://users.softlab.ntua.gr/~ttsiod/gnuplotStreaming.html

There's a little Perl script that can drive the plotting, and you just pipe your information in.

Since your data is being written to file, you may want to tail -f yourdata.dat and pipe that into the real-time plotter.

Also, because you're using the stdio file calls, you'd need to flush regularly (by calling fflush)

Obviously your simulation would be running in the background or in another shell. That way you could break out of the plotting at any time without interrupting the simulation.

Hope that's of some use to you.

Answer 4

There is a extensive library called DISLIN for scientific purpose. Avaliable even in Fortran language.

You can check examples in official website.

You can obtain it freely in DISLIN Homepage

Answer 5

OK, one solution, as you are writing out to a file, would be to just make a system() call when you write out to the file, and call gnuplot.

But, that means you should change the filename each time, but I fear if you do that that it won't look correct, since you are sending small amounts of data each time.

http://www.gnu.org/software/libc/manual/html_node/System-Calls.html

I have never used gnuplot, but if you look at this page (http://gnuplot-tricks.blogspot.com/) you may find some tricks that would enable this to work well.

But, I think, unless you are going to plot everything yourself, and skip gnuplot, then you may just need to wait, as you are.

You may find the C interface to gnuplot may help you:

http://ndevilla.free.fr/gnuplot/

Answer 6

Since you already know gnuplot, the simplest thing to do may be to just call gnuplot from your program and pipe the data to it:

FILE *gnuplot = popen("gnuplot", "w");
fprintf(gnuplot, "plot '-'\n");
for (i = 0; i < count; i++)
    fprintf(gnuplot, "%g %g\n", x[i], y[i]);
fprintf(gnuplot, "e\n");
fflush(gnuplot);