per

代码说明：

  function Px = per(x,n1,n2) PER Estimate the spectrum of a process using the periodogram ----------- USAGE Px = per(x,n1,n2) The spectrum of a process x is estimated using the periodogram. x : input sequence n1 : starting index, x(n1) n2 : ending index, x(n2) The periodogram is returned in Px using a linear scale. If n1 and n2 are not specified the periodogram of the entire sequence is computed.