MATLAB: Filter Design Basics

freqz

Hello.
I have a simple filter H(z) = 1 – z^-1
I can see my filter by writing:
b = [1 -1];
freqz(b,1);
what I would like to know is how to get this into the format for the filter design toolbox.
eg
d=fdesign.lowpass('N,Fc',80,0.5);
Hd=design(d);
freqz(Hd);
In my case, what would i be passing to fdesign.m, or design.m.
I know they should give the same answer, but with a different plot.
Or is it not possible to get the plotyy output if you know your filter coefficents?
thank you!!

Best Answer

Are you saying you already know the filter coefficients? In
H(z) = 1-z^{-1}
you have a high pass filter and you can create a filter object like design() would produce with:
     Hd = dfilt.df1([1 -1],1);
     fvtool(Hd);
If you do not already have the filter coefficients, then you can design the filter with fdesign and design and obtain the coefficients.
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