Graphics Programs Reference
In-Depth Information
causes the output
ans =
0.2268
0.1592
0.3292
0.2110
0.3683
0.2414
ans =
0.2268
0.1592
0
0
0
0
The vectors are identical up to element
y(end-m3+1)
, then the second vec-
tor
y4
contains zeros instead of true data values. Plotting the results with
subplot(2,1,1), plot(t,x3,'b-',t,y3,'g-')
subplot(2,1,2), plot(t,x3,'b-',t,y4,'g-')
or in one single plot,
plot(t,x3,'b-',t,y3,'g-',t,y4,'r-')
shows that the results of
conv
and
filter
are identical except for the upper
end of the data vector. These observations are important for our next steps in
signal processing, in particular if we are interested in leads and lags between
various components of signals.
6.6 Recursive and Nonrecursive Filters
Now we expand our nonrecursive fi lters by a recursive component, i.e., the
output
y
(
t
n
) depends on the fi lter input
x
(
t
), but also on previous output val-
ues
y
(
t
n
-1
),
y
(
t
n
-2
),
y
(
t
n
-3
). This fi lter requires the nonrecursive fi lter weights
b
i
,
but also the recursive fi lters weights
a
i
(Fig. 6.2). This fi lter can be described
by the
difference equation
.
Whereas this is a non-causal version of the difference equation, MATLAB
uses the causal indexing again,
