Rick Rick - 9 days ago 7
C++ Question

how to plot graph using GNUplot in C++

when I execute my program, I want my program to plot a graph and display on the screen. But I am not sure how do I do that.
Here is the example C++ code.

#include "stdafx.h"
# include <cstdlib>
# include <iostream>
# include <iomanip>
# include <cmath>

using namespace std;

# include "curve_plot.h"

int main();
int main()


{
int i;
int n;
double *x;
double *y;

cout << "\n";
cout << "CURVE_PLOT_PRB:\n";
cout << " Demonstrate how CURVE_PLOT can be used.\n";

// Set up some data to plot.

n = 51;
x = new double[n];
y = new double[n];
for (i = 0; i < 51; i++)
{
x[i] = (double)(i) / 10.0;
y[i] = x[i] * cos(x[i]);
}

// Send the data to curve_plot.
curve_plot(n, x, y, "curve_plot");

// Free memory.


delete[] x;
delete[] y;



return 0;
}


and here is the header file.

void curve_plot(int n, double x[], double y[], string name);

curve_plot.cpp

#include "stdafx.h"
# include <cstdlib>
# include <iostream>
# include <iomanip>
# include <fstream>
#include <string>
using namespace std;

# include "curve_plot.h"

void curve_plot(int n, double x[], double y[], string name)


{
string command_filename;
ofstream command_unit;
string data_filename;
ofstream data_unit;
int i;
string plot_filename;

// Write the data file.

data_filename = name + "_data.txt";
data_unit.open(data_filename.c_str());
for (i = 0; i < n; i++)
{
data_unit << x[i] << " "
<< y[i] << "\n";
}
data_unit.close();
cout << "\n";
cout << " Plot data written to the file \"" << data_filename << "\".\n";

// Write the command file.

command_filename = name + "_commands.txt";
command_unit.open(command_filename.c_str());
command_unit << "set term png\n";
plot_filename = name + ".png";
command_unit << "set output \"" << plot_filename << "\"\n";
command_unit << "set grid\n";
command_unit << "set style data lines\n";
command_unit << "unset key\n";
command_unit << "set xlabel '<---X--->'\n";
command_unit << "set ylabel '<---Y--->'\n";
command_unit << "set timestamp\n";
command_unit << "plot \"" << data_filename << "\" using 1:2 with lines lw 3\n";
command_unit << "quit\n";
command_unit.close();
cout << " Command data written to \"" << command_filename << "\".\n";

return;
}

Answer

What do you want, to run gnuplot from your C++ program or to run it after your C++ program execution? If it's the first, add

system("gnuplot gnuplot_command_file");

just before return statement. Of course, firstly you have to build a character string as a paramater of the system statement.

Otherwise, just execute in your command prompt

gnuplot your_command_file