sinft.txt

用VB实现的傅立叶变换谱方法 包括复数据快速傅立叶变换算法、实数据快速傅立叶变换算法1、实数据快速傅立叶变换算法2、快速正弦变换和余弦变换等

Sub SINFT(Y(), N)
    THETA = 3.14159265358979 / N
    WR = 1#
    WI = 0#
    WPR = -2# * Sin(0.5 * THETA) ^ 2
    WPI = Sin(THETA)
    Y(1) = 0#
    M = N / 2
    For J = 1 To M
        WTEMP = WR
        WR = WR * WPR - WI * WPI + WR
        WI = WI * WPR + WTEMP * WPI + WI
        Y1 = WI * (Y(J + 1) + Y(N - J + 1))
        Y2 = 0.5 * (Y(J + 1) - Y(N - J + 1))
        Y(J + 1) = Y1 + Y2
        Y(N - J + 1) = Y1 - Y2
    Next J
    Call REALFT(Y(), M, 1)
    Sum = 0#
    Y(1) = 0.5 * Y(1)
    Y(2) = 0#
    For J = 1 To N - 1 Step 2
        Sum = Sum + Y(J)
        Y(J) = Y(J + 1)
        Y(J + 1) = Sum
    Next J
End Sub