main.c

#include <stdlib.h>
#include <stdio.h>
#define NUM_POINTS 5
#define NUM_COMMANDS 2

int main()
{
  char * commandsForGnuplot[] = {"set title \"TITLEEEEE\"", "plot 'data.temp'"};
  double xvals[NUM_POINTS] = {1.2, 2.0, 3.0, 4.0, 4.5};
  double yvals[NUM_POINTS] = {4.8 ,3.0, 1.0, 3.0, 3.23};
  FILE * gnuplotPipe = popen ("gnuplot -persistent", "w");
  fprintf(gnuplotPipe, "plot '-' \n");
  int i;

  for (int i = 0; i < NUM_POINTS; i++)
    {
      fprintf(gnuplotPipe, "%lf %lf\n", xvals[i], yvals[i]);
    }

  fprintf(gnuplotPipe, "e");
  return 0;
}