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#include <graph.h>
#include <conio.h>
#include <stdlib.h>
#include <math.h>
#define DIM 512
float fXR[DIM + 1], fX[DIM + 1]
/*
*** WHEN COMPARING WITH THE TEXT, NOTE THAT IN THE C PROGRAMS **
******* FLOATING-POINT VARIABLES ARE PREFIXED WITH AN f, *******
************** INTEGER VARIABLES WITH AN i *********************
*/
void main (void)
{
/*
********* PROGRAM NO. 24 FAST FOURIER TRANSFORM (FFT) ***
*/
int iCount, iCount2, iCount3, iN =DIM, iM =9
iT, iLim1, iLim2, iLim3, iJ, iL, iY;
float fMax, fMag, fB1, fB2, fC1, fC2, fD,
fPI = 3.141593, fX1, fX2, fARG, fCos1, fSin1;
_clearscreen (_GCLEARSCREEN);
printf ("\n\nPROGRAM 24: Fast Fourier Transform (FFT)\n\n");
printf ("Press any key to start...\n\n);
getch();
for (iCount = 1; iCount <= iN; iCount++)
fXR[iCount] = fXI[iCount] = 0.0;
for (iCount = 1; iCount <= 32; iCount++)
fXR[iCount] = 1.0;
/*
******************** PLOT INPUT DATA **********************
*/
(iY=1,iY=1);
_setvideomode( _MAXRESMODE );
iY = 60;
for (iCount =1; iCount <= iN; iCount++)
{
moveto (iCount, iY);
lineto (iCount, (int)(iY - fXR[iCount] * 40.0 +0.5));
}
/*
**** SELECT TRANSFORM/ INVERSE TRANSFORM AND PLOT OFFSET ***
*/
for (iT = 1; iT > -2; iT -= 2)
{
iY += 60;
if (iT < 0)
fD = (float) iN;
else
fD = 1.0;
/*
***************** SHUFFLE INPUT DATA *******************
*/
iLim1 = iN - 1;
iLim2 = iN / 2;
iJ = 1;
for (iCount =1; iCount <= iLim1; iCount++)
{
if ((float) iCount <= ((float) iJ - 0.01))
{
fX1 = fXR[iJ];
fX2 = fXI[iJ];
fXR[iJ] = fXR[iCount];
fXI[iJ] = fXI[iCount];
fXR[iCount] = fX1;
fXI[iCount] = fX2;
}
iL = iLim2;
while (1)
{
if ((float)iL > ((float)(iJ) - 0.01))
break;
iJ -= iL;
iL /= 2;
}
iJ += iL
}
/*
************ IN PLACE TRANSFORMATION *******************
*/
for (iCount = 1; iCount <= iM; iCount++)
{
iLim1 = (int) pow (2, iCount-1);
iLim2 = (int) pow (2, (iM - iCount));
for (iCount2 = 1; iCount2 <= iLim2; iCount2++)
{
for (iCount3 =1; iCount3 <= iLim1; iCount3++)
{
iLim3 = (iCount3 - 1) + (iCount2 - 1) *
2 * iLim1 + 1;
fB1 = fXR[iLim3];
fB2 = fXI[iLim3];
fC1 = fXR[iLim3 + iLim1];
fC2 = FXI[iLim3 + iLim1];
fARG = 2.0 * fPI * (float) (iCount3 -1) *
(float) iLim2 / (float) iN;
fCos1 = cosI (fARG);
fSin1 = sinI (fARG);
fX1 = fC1 * fCos1 + fC2 * fSin1 *
(float) iT;
fX2 = (0.0 - fC1) * fSin1 * (float) iT +
fC2 * fCos1;
fXR[iLim3] = fB1 + fX1;
fXI[iLim3] = fB2 + fX2;
fXR[iLim3 + iLim1] = fB1 - fX1;
fXI[iLim3 + iLim1] = fB2 - fX2;
}
}
}
for (iCount = 1; iCount <= iN; iCount++)
{
fXR[iCount] /= fD;
fXI[iCount] /= fD;
}
/*
********** PLOT OUTPUT MAGNITUDE *******************
*/
fMax = 0.0;
for (iCount = 1; iCount <= 512 /* iN */; iCount++)
{
fMag = sqrt (pow (fXR[iCount], 2) +
pow (fXI[iCount],2));
if (fMag > fMax)
fMax = fMag;
}
for (iCount = 1; iCount <= 512 /*iN*/; iCount++)
{
_moveto (iCount+1, iY);
_lineto (iCount+1, (int)(iY -
(sqrt (pow (fXR[iCount], 2 +
pow (fXI [iCount], 2)) * 40.0 / fMax + 0.5)));
}
}
getch();
_setvideomode( _DEFAULTMODE );
/*
*****************************************************
*/
}
제가 C에 무뇌한이라서 간단하게 설명해주셔도 되고 길게 해주시면 더 감사 하겠습니다.
단락별로 해석이나 분석 좀 부탁 드릴게요
제발 부탁 드릴게요...
해석해서 제 이메일로 날려주시면 정말로 감사하겠습니다.
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