Designing Filter using fir1 in matlab

[Poopsilon]

So I'm trying to generate a filter fir1(31,0.25) and plot the normalized frequency response using -1 ≦ Θ ≦ 1, but I can't figure out where I am suppose to put in the angle theta, could someone help me out with this? Thanks.

 

[enjunear]

Read here for examples using fir1 to design a filter.
Window-based finite impulse response filter design - MATLAB

If you are supposed to plot vs. theta, then you are supposed to look at the phase response. I'd start with freqz to see both the mag and phase response of your filter. Make sure your filter looks correct (frequency response matches your inputs to fir1), then look at the phase. You should see lots of phase change near the corner frequencies of the filter.
Frequency response of filter - MATLAB

You could also use phasez, which should give you just the phase response of the digital filter.
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