?? fft.txt
字號:
快速傅里葉變換 要用C++ 才行吧 你可以用MATLAB來實現更方便點啊
此FFT 是用VC6.0編寫，由FFT.CPP；STDAFX.H和STDAFX.CPP三個文件組成，編譯成功。程序可以用文件輸入和輸出為文件。文件格式為TXT文件。測試結果如下：
輸入文件：8.TXT 或手動輸入
8 //N
1
2
3
4
5
6
7
8
輸出結果為：或保存為TXT文件。（8OUT.TXT）
8
(36,0)
(-4,9.65685)
(-4,4)
(-4,1.65685)
(-4,0)
(-4,-1.65685)
(-4,-4)
(-4,-9.65685)
下面為FFT.CPP文件：
// FFT.cpp : 定義控制臺應用程序的入口點。
#include "stdafx.h"
#include <iostream>
#include <complex>
#include <bitset>
#include <vector>
#include <conio.h>
#include <string>
#include <fstream>
using namespace std;
bool inputData(unsigned long &, vector<complex<double> >&); //手工輸入數據
void FFT(unsigned long &, vector<complex<double> >&); //FFT變換
void display(unsigned long &, vector<complex<double> >&); //顯示結果
bool readDataFromFile(unsigned long &, vector<complex<double> >&); //從文件中讀取數據
bool saveResultToFile(unsigned long &, vector<complex<double> >&); //保存結果至文件中
const double PI = 3.1415926;
int _tmain(int argc, _TCHAR* argv[])
{
vector<complex<double> > vecList; //有限長序列
unsigned long ulN = 0; //N
char chChoose = ' '; //功能選擇
//功能循環
while(chChoose != 'Q' && chChoose != 'q')
{
//顯示選擇項
cout << "\nPlease chose a function" << endl;
cout << "\t1.Input data manually, press 'M':" << endl;
cout << "\t2.Read data from file, press 'F':" << endl;
cout << "\t3.Quit, press 'Q'" << endl;
cout << "Please chose:";
//輸入選擇
chChoose = getch();
//判斷
switch(chChoose)
{
case 'm': //手工輸入數據
case 'M':
if(inputData(ulN, vecList))
{
FFT(ulN, vecList);
display(ulN, vecList);
saveResultToFile(ulN, vecList);
}
break;
case 'f': //從文檔讀取數據
case 'F':
if(readDataFromFile(ulN, vecList))
{
FFT(ulN, vecList);
display(ulN, vecList);
saveResultToFile(ulN, vecList);
}
break;
}
}
return 0;
}
bool Is2Power(unsigned long ul) //判斷是否是2的整數次冪
{
if(ul < 2)
return false;
while( ul > 1 )
{
if( ul % 2 )
return false;
ul /= 2;
}
return true;
}
bool inputData(unsigned long & ulN, vector<complex<double> >& vecList)
{
//題目
cout<< "\n\n\n==============================Input Data===============================" << endl;
//輸入N
cout<< "\nInput N:";
cin>>ulN;
if(!Is2Power(ulN)) //驗證N的有效性
{
cout<< "N is invalid (N must like 2, 4, 8, .....), please retry." << endl;
return false;
}
//輸入各元素
vecList.clear(); //清空原有序列
complex<double> c;
for(unsigned long i = 0; i < ulN; i++)
{
cout << "Input x(" << i << "):";
cin >> c;
vecList.push_back(c);
}
return true;
}
bool readDataFromFile(unsigned long & ulN, vector<complex<double> >& vecList) //從文件中讀取數據
{
//題目
cout<< "\n\n\n===============Read Data From File==============" << endl;
//輸入文件名
string strfilename;
cout << "Input filename:" ;
cin >> strfilename;
//打開文件
cout << "open file " << strfilename << "......." <<endl;
ifstream loadfile;
loadfile.open(strfilename.c_str());
if(!loadfile)
{
cout << "\tfailed" << endl;
return false;
}
else
{
cout << "\tsucceed" << endl;
}
vecList.clear();
//讀取N
loadfile >> ulN;
if(!loadfile)
{
cout << "can't get N" << endl;
return false;
}
else
{
cout << "N = " << ulN << endl;
}
//讀取元素
complex<double> c;
for(unsigned long i = 0; i < ulN; i++)
{
loadfile >> c;
if(!loadfile)
{
cout << "can't get enough infomation" << endl;
return false;
}
else
cout << "x(" << i << ") = " << c << endl;
vecList.push_back(c);
}
//關閉文件
loadfile.close();
return true;
}
bool saveResultToFile(unsigned long & ulN, vector<complex<double> >& vecList) //保存結果至文件中
{
//詢問是否需要將結果保存至文件
char chChoose = ' ';
cout << "Do you want to save the result to file? (y/n):";
chChoose = _getch();
if(chChoose != 'y' && chChoose != 'Y')
{
return true;
}
//輸入文件名
string strfilename;
cout << "\nInput file name:" ;
cin >> strfilename;
cout << "Save result to file " << strfilename << "......" << endl;
//打開文件
ofstream savefile(strfilename.c_str());
if(!savefile)
{
cout << "can't open file" << endl;
return false;
}
//寫入N
savefile << ulN << endl;
//寫入元素
for(vector<complex<double> >::iterator i = vecList.begin(); i < vecList.end(); i++)
{
savefile << *i << endl;
}
//寫入完畢
cout << "save succeed." << endl;
//關閉文件
savefile.close();
return true;
}
void FFT(unsigned long & ulN, vector<complex<double> >& vecList)
{
//得到冪數
unsigned long ulPower = 0; //冪數
unsigned long ulN1 = ulN - 1;
while(ulN1 > 0)
{
ulPower++;
ulN1 /= 2;
}
//反序
bitset<sizeof(unsigned long) * 8> bsIndex; //二進制容器
unsigned long ulIndex; //反轉后的序號
unsigned long ulK;
for(unsigned long p = 0; p < ulN; p++)
{
ulIndex = 0;
ulK = 1;
bsIndex = bitset<sizeof(unsigned long) * 8>(p);
for(unsigned long j = 0; j < ulPower; j++)
{
ulIndex += bsIndex.test(ulPower - j - 1) ? ulK : 0;
ulK *= 2;
}
if(ulIndex > p)
{
complex<double> c = vecList[p];
vecList[p] = vecList[ulIndex];
vecList[ulIndex] = c;
}
}
//計算旋轉因子
vector<complex<double> > vecW;
for(unsigned long i = 0; i < ulN / 2; i++)
{
vecW.push_back(complex<double>(cos(2 * i * PI / ulN) , -1 * sin(2 * i * PI / ulN)));
}
for(unsigned long m = 0; m < ulN / 2; m++)
{
cout<< "\nvW[" << m << "]=" << vecW[m];
}
//計算FFT
unsigned long ulGroupLength = 1; //段的長度
unsigned long ulHalfLength = 0; //段長度的一半
unsigned long ulGroupCount = 0; //段的數量
complex<double> cw; //WH(x)
complex<double> c1; //G(x) + WH(x)
complex<double> c2; //G(x) - WH(x)
for(unsigned long b = 0; b < ulPower; b++)
{
ulHalfLength = ulGroupLength;
ulGroupLength *= 2;
for(unsigned long j = 0; j < ulN; j += ulGroupLength)
{
for(unsigned long k = 0; k < ulHalfLength; k++)
{
cw = vecW[k * ulN / ulGroupLength] * vecList[j + k + ulHalfLength];
c1 = vecList[j + k] + cw;
c2 = vecList[j + k] - cw;
vecList[j + k] = c1;
vecList[j + k + ulHalfLength] = c2;
}
}
}
}
void display(unsigned long & ulN, vector<complex<double> >& vecList)
{
cout << "\n\n===========================Display The Result=========================" << endl;
for(unsigned long d = 0; d < ulN;d++)
{
cout << "X(" << d << ")\t\t\t = " << vecList[d] << endl;
}
}
下面為STDAFX.H文件：
// stdafx.h : 標準系統包含文件的包含文件，
// 或是常用但不常更改的項目特定的包含文件
#pragma once
#include <iostream>
#include <tchar.h>
// TODO: 在此處引用程序要求的附加頭文件
下面為STDAFX.CPP文件：
// stdafx.cpp : 只包括標準包含文件的源文件
// FFT.pch 將成為預編譯頭
// stdafx.obj 將包含預編譯類型信息
#include "stdafx.h"
// TODO: 在 STDAFX.H 中
//引用任何所需的附加頭文件，而不是在此文件中引用?? 快捷鍵說明
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