Here's another way of calling gnuplot. I like this method because it provides a standalone function that plots your results. Here's the code:

#include <stdio.h>

#include <stdlib.h>

#include <math.h>

void plotResults(double* xData, double* yData, int dataSize);

int main() {

int i = 0;

int nIntervals = 100;

double intervalSize = 1.0;

double stepSize = intervalSize/nIntervals;

double* xData = (double*) malloc((nIntervals+1)*sizeof(double));

double* yData = (double*) malloc((nIntervals+1)*sizeof(double));

xData[0] = 0.0;

double x0 = 0.0;

for (i = 0; i < nIntervals; i++) {

x0 = xData[i];

xData[i+1] = x0 + stepSize;

}

for (i = 0; i <= nIntervals; i++) {

x0 = xData[i];

yData[i] = sin(x0)*cos(10*x0);

}

plotResults(xData,yData,nIntervals);

return 0;

}

void plotResults(double* xData, double* yData, int dataSize) {

FILE *gnuplotPipe,*tempDataFile;

char *tempDataFileName;

double x,y;

int i;

tempDataFileName = "tempData";

gnuplotPipe = popen("c:\\gnuplot\\bin\\pgnuplot -persist","w");

if (gnuplotPipe) {

fprintf(gnuplotPipe,"plot \"%s\" with lines\n",tempDataFileName);

fflush(gnuplotPipe);

tempDataFile = fopen(tempDataFileName,"w");

for (i=0; i <= dataSize; i++) {

x = xData[i];

y = yData[i];

fprintf(tempDataFile,"%lf %lf\n",x,y);

}

fclose(tempDataFile);

printf("press enter to continue...");

getchar();

remove(tempDataFileName);

fprintf(gnuplotPipe,"exit \n");

} else {

printf("gnuplot not found...");

}

}

This code should run as is. Of course, feel free to take the plot function and use it in your own codes.

Cite as:

Saad, T. "Calling Gnuplot from c Using Pipes... Again!".
Weblog entry from
Please Make A Note.
http://pleasemakeanote.blogspot.ca/2009/05/calling-gnuplot-from-c-using-pipes.html