I am trying to perform a simple simulation in Matlab. I have a random signal x and a filter transfer function. What is the proper usage of the filter function?
x = rand(100,1);
syms z;
Pnum = (1-0.1*z^-1);
Pdenum = (1-0.9*z^-1);
y = filter(Pnum, Pdenum, x);
This throws the error
"Undefined function 'filter' for input arguments of type 'sym'."
I understand that it's complaining about the z variable. How should I go about solving it?
The filter command is not built to take symbolic data types. It takes the raw filter coefficients as input. What it looks like you are trying to define is a difference equation where the b coefficients are . .
b = [1 0.1];
and the a coefficients are
a = [1 0.9];
you can then filter the signal as follows
y = filter(b,a,x)
The freqz command reveals that this is a strange high pass filter with some gain . .
freqz(b,a)
Is this what you are trying to achieve?
If you reverse the coefficients so
b = [1 0.9];
a = [1 0.1];
...you end up with a low pass filter with some gain
freqz(b,a)
