stft                  package:e1071                  R Documentation

_C_o_m_p_u_t_e_s _t_h_e _S_h_o_r_t _T_i_m_e _F_o_u_r_i_e_r _T_r_a_n_s_f_o_r_m _o_f _a _V_e_c_t_o_r

_D_e_s_c_r_i_p_t_i_o_n:

     This function computes the Short Time Fourier Transform of a given
     vector 'X'. 

     First, time-slices of length 'win' are extracted from the vector.
     The shift of one time-slice to the next one is given by 'inc'. The
     values of these time-slices are smoothed by mulitplying them with
     a window function specified in 'wtype'. For the thus obtained
     windows, the Fast Fourier Transform is computed.

_U_s_a_g_e:

     stft(X, win=min(80,floor(length(X)/10)), inc=min(24,
     floor(length(X)/30)), coef=64, wtype="hanning.window")

_A_r_g_u_m_e_n_t_s:

       X: The vector from which the stft is computed.

     win: Length of the window. For long vectors the default window
          size is 80, for short vectors the window size is chosen so
          that 10 windows fit in the vector.

     inc: Increment by which the window is shifted. For long vectors
          the default increment is 24, for short vectors the increment
          is chosen so that 30 increments fit in the vector.

    coef: Number of Fourier coefficients

   wtype: Type of window used

_V_a_l_u_e:

     Object of type stft. Contains the values of the stft and
     information about the parameters. 

  values: A matrix containing the results of the stft. Each row of the
          matrix contains the 'coef' Fourier coefficients of one
          window.

windowsize: The value of the parameter 'win'

increment: The value of the parameter 'inc'

windowtype: The value of the parameter 'wtype'

_A_u_t_h_o_r(_s):

     Andreas Weingessel

_S_e_e _A_l_s_o:

     plot.stft

_E_x_a_m_p_l_e_s:

     x<-rnorm(500)
     y<-stft(x)
     plot(y)

