INTERACTIVE SIGNAL DEMO16NYNU2


      You are seeing discrete samples of a periodic waveform (above) and the 

      absolute value of its discrete Fourier transform (DFT), obtained using

      a fast Fourier transform (FFTMORSU2) algorithm (below).  

      In the lower plot, frequencies from 0 to 100 Hertz are displayed.

      The DFT at negative frequencies is a mirror image of the DFT at positive

      frequencies.  The sampling rate is 200 Hertz which means the "Nyquist

      frequency" is 100 Hertz.  The DFT at frequencies above the Nyquist 

      frequency is the same as the DFT at lower (negative) frequencies.



      Click and drag a point on the waveform displayed in the upper plot

      to move that point to a new location, thereby setting a new fundamental

      frequency and amplitude.



      Use the pop-up menu in the bottom left of the figure window to change 

      the shape of the waveform.  The possible wave shapes are sinusoidal, 

      square, and sawtooth.



      The fundamental frequency of the waveform is given in the editable

      text box in the middle of the bottom row.  You can change this

      fundamental frequency by clicking in the text box and editing

      the number there, and then pressing RETURNKS5UQA.  The fundamental is also 

      changed when the waveform is altered by clicking and dragging.



      If the Signal Processing Toolbox is installed, then the menu entitled

      "Window" allows you to select a window function.  This window is 

      multiplied by the time waveform prior to taking the DFT.  To display

      the current window function in another figure window, select the menu 

      item "Show window...".