Function: demo_phaseplot
DEMO_PHASEPLOT  Give demos of nice phaseplots

  This script creates a synthetic signal and then uses PHASEPLOT on it,
  using several of the possible options.

  For real-life signal only small parts should be analyzed. In the chosen
  demo the fundamental frequency of the speaker can be nicely seen.

  Figure 1: Synthetic signal

     Compare this to the pictures in reference 2 and 3. In 
     the first two figures a synthetic signal is analyzed. It consists of a 
     sinusoid, a small Delta peak, a periodic triangular function and a 
     Gaussian. In the time-invariant version in the first part the periodicity 
     of the sinusoid can be nicely seen also in the phase coefficients. Also
     the points of discontinuities can be seen as asymptotic lines approached
     by parabolic shapes. In the third part both properties, periodicity and 
     discontinuities can be nicely seen. A comparison to the spectogram shows 
     that the rectangular part in the middle of the signal can be seen by the
     phase plot, but not by the spectogram.

     In the frequency-invariant version, the fundamental frequency of the
     sinusoid can still be guessed as the position of an horizontal
     asymptotic line.

  Figure 2: Synthetic signal, thresholded.

     This figure shows the same as Figure 1, except that values with low
     magnitude has been removed.

  Figure 3: Speech signal.

     The figure shows a part of the 'linus' signal. The fundamental
     frequency of the speaker can be nicely seen.

  References:
    R. Carmona, W. Hwang, and B. Torresani. Multiridge detection and
    time-frequency reconstruction. IEEE Trans. Signal Process.,
    47:480--492, 1999.
    
    R. Carmona, W. Hwang, and B. Torresani. Practical Time-Frequency
    Analysis: continuous wavelet and Gabor transforms, with an
    implementation in S, volume 9 of Wavelet Analysis and its Applications.
    Academic Press, San Diego, 1998.
    
    A. Grossmann, M. Holschneider, R. Kronland-Martinet, and J. Morlet.
    Detection of abrupt changes in sound signals with the help of wavelet
    transforms. Inverse Problem, pages 281--306, 1987.
    

Url: http://ltfat.github.io/doc/demos/demo_phaseplot.html

Package: ltfat