Page 64 - Basics of MATLAB and Beyond

clf
polar(t,gdb)

In this case you must use a modified version of polar that interprets
a zero radius as a 0 dB value which should go at the outer limit of the
plot. Negative decibel values should appear at smaller radii. I have
implemented these ideas in the m-file negpolar (see companion soft-
ware):

negpolar(t,gdb)

The negpolar function also omits the solid outer circle which, like the
box drawn around matlab’s default plot output, unnecessarily frames
the plot and can obscure the data that you are trying to display. A faint
dotted grid is enough to put the plotted points in context. I will say
more about this in the section on Handle Graphics later (see page 65).

17 Fourier Transform

A theorem of mathematics says, roughly, that any function can be repre-
sented as a sum of sinusoids of different amplitudes and frequencies. The
Fourier transform is the mathematical technique of finding the ampli-
tudes and frequencies of those sinusoids. The Discrete Fourier Transform
(DFT) is an algorithm that calculates the Fourier transform for numer-
ical data. The Fast Fourier Transform is an efficient implementation of
the DFT. The following functions are available in matlab to do Fourier
transforms and related operations:

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