multiple line-plots in gnuplot using C-CodePudding

For a terminal application written in C I need to plot (in the terminal) two tables as line plots. To do this I use (following e.g. gnu tutorial)

 FILE *gnuplot = popen("gnuplot", "w");
 ...
  fprintf(gnuplot, "plot '-' u 1:2 t 'data1' w lp lt 0\n");
      for (int i = 0; i < lines;   i) {
        fprintf(gnuplot,"%f %f \n", x[i] - x[0], y[i]);
    }
fprintf(gnuplot, "\n");
  fprintf(gnuplot, "t 'data2' lt 2\n");
    for (int i = 0; i < lines;   i) {
        fprintf(gnuplot,"%f %f \n", x[i] - x[0], 0.4*(x[i] - c0)/c1);
    }
    fprintf(gnuplot, "e\n");
    fflush(gnuplot);

The problem is that the data is plotted as one data block instead of two different ones. I expected to have a separation by using the line

fprintf(gnuplot, "t 'data2' lt 2\n");

which seems not to be the case. What is wrong in this code?

CodePudding user response：

You probably want to do the following. Each inline data has to be terminated by an e. In gnuplot console it would be:

plot '-' u 1:2 t 'data1' w lp lt 0, '' u 1:2 t 'data2' lt 2
 1  0.1
 2  0.2
 3  0.3
 4  0.4
e
11  0.5
12  0.6
13  0.7
14  0.8
e

Check help inline data and help special-filenames. Although, to my opinion it is a bit confusing and suitable examples are missing. Maybe you can find them elsewhere.