Programming Forums > Application Development > C++

can342man · Jan 27th, 2006, 8:33 AM

Hi everyone,

I have written a MC numerical integration program for solving indefinite integrals. The problem I am facing is trying to dump the output of the numbers generated to a file so I can plot it using Excel or other spreadsheet. I have a function for the output but it doesn't seem to work properly. It only gives me one set of number. I need the entire set of numbers generated (>10000) by the program to analyze and plot in a spreadsheet.

Also is there a particular format I should output the file so that it can be easily read by any spreadsheet program such as (.csv) format?

(Toggle Plain Text)

#include <iostream>
#include <fstream>
#include <cstdlib>      // random function rand() and srand()
#include <cmath>        // pow() and sqrt() functions
using namespace std;

float fileout(double resultF4, double resultErr4);

main() {
        double x, func = 0.0, func2 = 0.0, resultF, errorF, resultErr;
        int itry, ntry;
        cout << "Input the number of MC trials" << "\n";
        cin >> ntry;

// seed rand() function with void srand( (unsigned) time((int *)0) ); dependant on time program run

        srand((unsigned)time((long *)0));
        for (itry=0; itry<ntry; itry++) {

// random generate to largest number (2^31 - 1) RAND_MAX

                x = rand()/(float)RAND_MAX;
                func = func + pow(x,2);         // function to be evaluated is parabola of x^2
                func2 = func2 + pow(x,4);
                errorF = sqrt(func - func2);
                resultF = func/ntry;
                resultErr = errorF/ntry;
                fileout(resultF, resultErr);
        }
}

float fileout(double resultF2, double resultErr2)
{
        ofstream out("output.dat");
        if (!out) {
                cout << "Cannot open file." << "\n";
                return 1;
        }

        out << "Function  = " << resultF2 << " " << " Error  = " << resultErr2 << "\n";
        out.close();
}

I am using a Debian Linux with GNU C/C++.

Anyone can help I really appreciate it.

Thank you.

nnxion · Jan 27th, 2006, 9:58 AM

Does it work with the following?

(Toggle Plain Text)

#include <iostream>
#include <fstream>
#include <cstdlib>
#include <cmath>
#include <ctime>

using namespace std;

// prototypes
int fileout(double resultF4, double resultErr4);

int main()
{
	double x, func = 0.0, func2 = 0.0, resultF, errorF, resultErr;
	int itry, ntry;
	cout << "Input the number of MC trials:" << endl;
	cin >> ntry;

	srand((unsigned)time(0));
	for (itry=0; itry<ntry; itry++)
	{
		x = rand()/(float)RAND_MAX;
		func = func + pow(x,2);
		func2 = func2 + pow(x,4);
		errorF = sqrt(func - func2);
		resultF = func/ntry;
		resultErr = errorF/ntry;
		fileout(resultF, resultErr);
	}
	return 0;
}

int fileout(double resultF2, double resultErr2)
{
	ofstream out("output.dat");
	if (!out)
	{
			cout << "Cannot open file." << endl;
			return 1;
	}

	out << "Function  = " << resultF2 << " " << " Error  = " << resultErr2 << endl;
	out.close();
	return 0;
}

If not, you might want to flush it with sync(), but it should work with endl.

nnxion · Jan 27th, 2006, 11:11 AM

Ohh I reread what you said, and if it's supposed to outputting it all, then you might want to put it in a loop instead of just once doing:

(Toggle Plain Text)

out << "Function  = " << resultF2 << " " << " Error  = " << resultErr2 << endl;

can342man · Jan 27th, 2006, 12:13 PM

Thanks nnxion for the tip, putting in the for loop around the out statement works and prints out all the data into the output file.

However, there is a problem, all the data is identically the same (it is supposed to be different), it seems that when the function "fileout" is called each time during the for loop in the main section, it passes the same data to the subroutine. Do you or anyone else know how to fix this part.

Really appreciate it.
Thank you.

Jerkstore · Jan 27th, 2006, 4:21 PM

the way you have it set up right now is that it opens the file every time the output function is called and then rewrites the file with the new data.

you can either open the file and append the new data to the end, or open the file once and write a vector or list of data to it after all the calculations are done.

...or you could open the file before your for loop and close it after, but it's generally not good practice to have your file get opened outside of your actual output method

Jan 27th, 2006, 8:33 AM	#1
can342man Newbie Join Date: Jan 2006 Location: London, Ontario, Canada Posts: 16 Rep Power: 0	Numerical data output to a file Hi everyone, I have written a MC numerical integration program for solving indefinite integrals. The problem I am facing is trying to dump the output of the numbers generated to a file so I can plot it using Excel or other spreadsheet. I have a function for the output but it doesn't seem to work properly. It only gives me one set of number. I need the entire set of numbers generated (>10000) by the program to analyze and plot in a spreadsheet. Also is there a particular format I should output the file so that it can be easily read by any spreadsheet program such as (.csv) format? (Toggle Plain Text) #include <iostream> #include <fstream> #include <cstdlib> // random function rand() and srand() #include <cmath> // pow() and sqrt() functions using namespace std; float fileout(double resultF4, double resultErr4); main() { double x, func = 0.0, func2 = 0.0, resultF, errorF, resultErr; int itry, ntry; cout << "Input the number of MC trials" << "\n"; cin >> ntry; // seed rand() function with void srand( (unsigned) time((int )0) ); dependant on time program run srand((unsigned)time((long )0)); for (itry=0; itry<ntry; itry++) { // random generate to largest number (2^31 - 1) RAND_MAX x = rand()/(float)RAND_MAX; func = func + pow(x,2); // function to be evaluated is parabola of x^2 func2 = func2 + pow(x,4); errorF = sqrt(func - func2); resultF = func/ntry; resultErr = errorF/ntry; fileout(resultF, resultErr); } } float fileout(double resultF2, double resultErr2) { ofstream out("output.dat"); if (!out) { cout << "Cannot open file." << "\n"; return 1; } out << "Function = " << resultF2 << " " << " Error = " << resultErr2 << "\n"; out.close(); } #include <iostream> #include <fstream> #include <cstdlib> // random function rand() and srand() #include <cmath> // pow() and sqrt() functions using namespace std; float fileout(double resultF4, double resultErr4); main() { double x, func = 0.0, func2 = 0.0, resultF, errorF, resultErr; int itry, ntry; cout << "Input the number of MC trials" << "\n"; cin >> ntry; // seed rand() function with void srand( (unsigned) time((int )0) ); dependant on time program run srand((unsigned)time((long )0)); for (itry=0; itry<ntry; itry++) { // random generate to largest number (2^31 - 1) RAND_MAX x = rand()/(float)RAND_MAX; func = func + pow(x,2); // function to be evaluated is parabola of x^2 func2 = func2 + pow(x,4); errorF = sqrt(func - func2); resultF = func/ntry; resultErr = errorF/ntry; fileout(resultF, resultErr); } } float fileout(double resultF2, double resultErr2) { ofstream out("output.dat"); if (!out) { cout << "Cannot open file." << "\n"; return 1; } out << "Function = " << resultF2 << " " << " Error = " << resultErr2 << "\n"; out.close(); } I am using a Debian Linux with GNU C/C++. Anyone can help I really appreciate it. Thank you.

Jan 27th, 2006, 9:58 AM	#2
nnxion Programming Guru Join Date: Jun 2005 Location: elemental plane Posts: 1,429 Rep Power: 5	Does it work with the following? (Toggle Plain Text) #include <iostream> #include <fstream> #include <cstdlib> #include <cmath> #include <ctime> using namespace std; // prototypes int fileout(double resultF4, double resultErr4); int main() { double x, func = 0.0, func2 = 0.0, resultF, errorF, resultErr; int itry, ntry; cout << "Input the number of MC trials:" << endl; cin >> ntry; srand((unsigned)time(0)); for (itry=0; itry<ntry; itry++) { x = rand()/(float)RAND_MAX; func = func + pow(x,2); func2 = func2 + pow(x,4); errorF = sqrt(func - func2); resultF = func/ntry; resultErr = errorF/ntry; fileout(resultF, resultErr); } return 0; } int fileout(double resultF2, double resultErr2) { ofstream out("output.dat"); if (!out) { cout << "Cannot open file." << endl; return 1; } out << "Function = " << resultF2 << " " << " Error = " << resultErr2 << endl; out.close(); return 0; } #include <iostream> #include <fstream> #include <cstdlib> #include <cmath> #include <ctime> using namespace std; // prototypes int fileout(double resultF4, double resultErr4); int main() { double x, func = 0.0, func2 = 0.0, resultF, errorF, resultErr; int itry, ntry; cout << "Input the number of MC trials:" << endl; cin >> ntry; srand((unsigned)time(0)); for (itry=0; itry<ntry; itry++) { x = rand()/(float)RAND_MAX; func = func + pow(x,2); func2 = func2 + pow(x,4); errorF = sqrt(func - func2); resultF = func/ntry; resultErr = errorF/ntry; fileout(resultF, resultErr); } return 0; } int fileout(double resultF2, double resultErr2) { ofstream out("output.dat"); if (!out) { cout << "Cannot open file." << endl; return 1; } out << "Function = " << resultF2 << " " << " Error = " << resultErr2 << endl; out.close(); return 0; } If not, you might want to flush it with sync(), but it should work with endl. __________________ "Employ your time in improving yourself by other men's writings, so that you shall gain easily what others have labored hard for." -- Socrates

Jan 27th, 2006, 11:11 AM	#3
nnxion Programming Guru Join Date: Jun 2005 Location: elemental plane Posts: 1,429 Rep Power: 5	Ohh I reread what you said, and if it's supposed to outputting it all, then you might want to put it in a loop instead of just once doing: (Toggle Plain Text) out << "Function = " << resultF2 << " " << " Error = " << resultErr2 << endl; out << "Function = " << resultF2 << " " << " Error = " << resultErr2 << endl; __________________ "Employ your time in improving yourself by other men's writings, so that you shall gain easily what others have labored hard for." -- Socrates

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Jan 27th, 2006, 12:13 PM	#4
can342man Newbie Join Date: Jan 2006 Location: London, Ontario, Canada Posts: 16 Rep Power: 0	Thanks nnxion for the tip, putting in the for loop around the out statement works and prints out all the data into the output file. However, there is a problem, all the data is identically the same (it is supposed to be different), it seems that when the function "fileout" is called each time during the for loop in the main section, it passes the same data to the subroutine. Do you or anyone else know how to fix this part. Really appreciate it. Thank you.

Jan 27th, 2006, 4:21 PM	#5
Jerkstore Newbie Join Date: Dec 2005 Posts: 12 Rep Power: 0	the way you have it set up right now is that it opens the file every time the output function is called and then rewrites the file with the new data. you can either open the file and append the new data to the end, or open the file once and write a vector or list of data to it after all the calculations are done. ...or you could open the file before your for loop and close it after, but it's generally not good practice to have your file get opened outside of your actual output method

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Programming Forums > Application Development > C++

Numerical data output to a file