gunplot demo

 1 //author : Leon yangli0534@gmail.com
 2 
 3 #include <stdlib.h>
 4 #include <stdio.h>
 5 #include <math.h>
 6 #define NUM_POINTS 500
 7 #define NUM_COMMANDS 2
 8 
 9 int main()
10 {
11     char * commandsForGnuplot[] = {"set title \"gunplot demo\"", "plot ‘data.temp‘"};
12     double fs = 1000000.0;
13     double f0 = 10000.0;
14     double xvals[NUM_POINTS] = {1.0, 2.0, 3.0, 4.0, 5.0};
15     double yvals[NUM_POINTS] = {5.0 ,3.0, 1.0, 3.0, 5.0};
16     FILE * temp = fopen("data.temp", "w");
17     /*Opens an interface that one can use to send commands as if they were typing into the
18      *     gnuplot command line.  "The -persistent" keeps the plot open even after your
19      *     C program terminates.
20      */
21     FILE * gnuplotPipe = popen ("gnuplot -persistent", "w");
22     int i;
23     for (i=0; i < NUM_POINTS; i++)
24     {
25     xvals[i] = i/fs;
26     yvals[i] = sin(2*M_PI*f0*xvals[i]);
27     }
28     for (i=0; i < NUM_POINTS; i++)
29     {
30     fprintf(temp, "%lf %lf \n", xvals[i], yvals[i]); //Write the data to a temporary file
31     }
32 
33     for (i=0; i < NUM_COMMANDS; i++)
34     {
35     fprintf(gnuplotPipe, "%s \n", commandsForGnuplot[i]); //Send commands to gnuplot one by one.
36     }
37     return 0;
38 }