; This batch file creates a plot of the magnitude and phase
; of the simulated signal used in the example from Chapter 13,
; "Signal Processing", of _Using IDL_.

@sigprc01  ; compute time data sequence u

V = FFT(U) ; compute spectrum v

F = FINDGEN(N/2+1) / (N*delt) ; f = [0.0, 1.0/(N*delt), ... , 1.0/(2.0*delt)]

mag = ABS(V(0:N/2)); magnitude of first half of v

phi = ATAN(V(0:N/2)) ; phase of first half of v

; log plots of magnitude in dB and phase in degrees

!P.MULTI = [0, 1, 2] ; set up for two plots in window

PLOT, F, 20*ALOG10(mag), YTITLE='Magnitude in dB', $
    XTITLE='Frequency in cycles / second', /XLOG, $
    XRANGE=[1.0,1.0/(2.0*delt)], XSTYLE=1, TITLE='Spectrum of u(k)'

PLOT, F, phi/!DTOR, YTITLE='Phase in degrees', $
    YRANGE=[-180,180], YSTYLE=1, YTICKS=4, YMINOR=3, $
    XTITLE='Frequency in cycles / second', /XLOG, $
    XRANGE=[1.0,1.0/(2.0*delt)], XSTYLE=1

!P.MULTI = 0