Graphics Programs Reference

In-Depth Information

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 eQcient implementation of

the DFT. The following functions are available in matlab to do Fourier

transforms and related operations: