Writing a list of data values to a .dat file to plot in GNUplot (in C)

Question

Hiya, I have written two different methods to numerically differentiate a function and I am looking for a way to compare them. I have installed GNUPlot and would like to make a file (e.g. approximations.dat) for it to plot. At the moment my programn prints a series of columns with x-coordinate, approximation 1, approximation 2 and actual value like this:

x-coord      approx 1      approx 2      actual  
x-coord      approx 1      approx 2      actual  
x-coord      approx 1      approx 2      actual  
x-coord      approx 1      approx 2      actual  
 ...            ...           ...          ...

Is there a way for me to make this into a file which can be input easily into GUPlot? Many thanks.

Jack

Answer 1

This is already a format well suited for gnuplot. Look up help plot using from the gnuplot prompt.

In order to get this into a file, you can either pipe the standard output from your program (e.g. in Unix-like systems with yourprog > file.dat), or use the C function fprintf (with fopen and fclose).

Answer 2

This tutorial should help you http://www.duke.edu/~hpgavin/gnuplot.html