DFT on OpenOffice Calc

dft.bas

Sub FourierTrans

	Dim oSelFile As Object
	Dim oSelSheet As Object
	Dim uiLenStrm As Integer
	Dim uiLenCoef As Integer
	Dim uiLenOut As Integer
	Dim fsumBuff As Double
	oSelFile = ThisComponent
	
	rem // get stream
	rem // signalのシートのA列に信号，B1に信号の長さを入れておく．spectのシートを作っておく
	oSelSheet = oSelFile.Sheets.getByName("signal")
	uiLenStrm = oSelSheet.getCellByPosition(1, 0 ).Value
	Dim mfStream( uiLenStrm+1) as Double
	for uilp = 0 to uiLenStrm
		mfStream(uilp) =  oSelSheet.getCellByPosition(0, uilp ).Value
	next uilp
		
	rem // calculation Descrete Fourier Transform
	Dim mfResultR( uiLenStrm+1) as Double
	Dim mfResultI( uiLenStrm+1) as Double
	
	
	for uilpA = 0 to uiLenStrm-1
		fsumBuffR = 0.0
		fsumBuffI = 0.0
		for uilpB = 0 to uiLenStrm-1
			fsumBuffR = fsumBuffR + mfStream(uilpB)*cos(2*PI*uilpA*uilpB/uiLenStrm)
			fsumBuffI = fsumBuffI + mfStream(uilpB)*sin(2*PI*uilpA*uilpB/uiLenStrm)
		next uilpB
		mfResultR(uilpA)=fsumBuffR
		mfResultI(uilpA)=fsumBuffI
	next uilpA

	oSelSheet = oSelFile.Sheets.getByName("spect")
	
	for uilpA = 0 to uiLenStrm-1
		oSelSheet.getCellByPosition(0, uilpA ).Value = (uilpA)/uiLenStrm
		oSelSheet.getCellByPosition(1, uilpA ).Value = mfResultR(uilpA)
		oSelSheet.getCellByPosition(2, uilpA ).Value = mfResultI(uilpA)
		oSelSheet.getCellByPosition(3, uilpA ).Value = mfResultR(uilpA)*mfResultR(uilpA)+mfResultI(uilpA)*mfResultI(uilpA)
		rem oSelSheet.getCellByPosition(4, uilpA ).Value = atan(mfResultI(uilpA)/mfResultR(uilpA) + (mfResultI(uilpA)*mfResultR(uilpA))=0)
		rem oSelSheet.getCellByPosition(4, uilpA ).Value = atan(mfResultI(uilpA)/mfResultR(uilpA) )
	next uilpA


End Sub