Question

This is my first post and I’m quite a novice on C++ and compiling in general.

I’m compiling a program which requires some graphs to be drawn. The program create a .dat file and then i should open gnuplot and write plot ‘.dat’. That’s fine.

Is there a way to make gnuplot automatically open and show me the plot I need? I should use some system() function in the code to call gnuplot but how can I make him plot what I need?

Sorry for my non-perfect English :s

Thanks for the attention anyway!

Answer 1

Depending on your OS, you might be able to use popen(). This would let you spawn a gnuplot process and just just write to it like any other FILE*.

If you have datapoints to plot, you can pass them inline with the plot ‘-‘ … option. Similarly, you may want to explore set data style points/lines/linespoints/etc options.

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Without pause or persist, gnuplot will terminate upon end-of-input-stream. In your example case, that would be when the end of the file is reached.

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To produce (write) an output file (graph), use:

set terminal png small set output 'filename.png' 

There’s lots of options to set terminal. Png is usually there. If not, perhaps gif, tiff, or jpeg?

Watch out for overwriting the file!

You may want to use set size 2,2 to make a larger graph. Some set terminal variants also allow you to specify the size.