Help with library implementation

[kkg]

Hi all,

I'm attempting to write a program that will compute the FFTs of a data set 32 point accross the band froma user-specified file and will output the results to another file. I downlaoded the FFTW library, I am just having trouble figuring out how ot use it/implement it in my program. This is what I have so far:

#include <iostream>
#include <fstream>

using namespace std;

int main()
{
	char filename[101];
	ifstream existtest, infile;
	ofstream opentest, outfile;			
	
	cout << "Copyright: 3 Aug 2011 Karla Guardado\n\n";
    cout << "Program takes data from user-specified file and computes FFTs\n";
    cout << "(Fast Fourier Transforms) on data. Outputs FFTs to FFTdata.xls.\n";
    cout << endl;
    
    cout << "Enter file name. (Type name, extension included, then press <ENTER>.)";
    cout << endl << endl << "File name: ";
	cin >> filename;
	
	existtest.open(filename);
	
	if (existtest.fail()) {
		existtest.close();
		cout << "ERROR: File does not exsist. Exiting.\n" << endl;
		system ("pause");
		return 0;
	}
	
	existtest.close();
    opentest.open(filename);
	
	if (opentest.fail()) {
		opentest.close();
        cout << "ERROR: File failed to open. Exiting.";
		system ("pause");
		return 0;
	}
	
    //read, take FFTs on data, output to outfile
	
    outfile.open("FFTdata.xls");
	
	system ("pause");
	return 0;
}

Any help would be greatly appreciated!

Thanks!