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# how to plot magniture and phase response of a filter?

Asked by LeBron on 10 Apr 2013

Hey everyone heres the question: http://img42.imageshack.us/img42/3236/capturezih.jpg I cant seem to get the plots to work

Heres my matlab code

```    w=0:0.001:pi;
Hw=(0.1*(exp(1j*w)-1))/(exp(1j*w)+0.8);
figure (1)
subplot (2,1,1)
plot(w,abs(Hw))
subplot (2,1,2)
plot(w,angle(Hw))```

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Answer by Teja Muppirala on 10 Apr 2013

You need to do elementwise division, use "./" instead of "/"

```Hw=(0.1*(exp(1j*w)-1))./(exp(1j*w)+0.8);
```

## 1 Comment

LeBron on 10 Apr 2013

One more question related to the same question: http://img23.imageshack.us/img23/7905/capturelc.jpg

```if true
n=1:5:100;
x=cos(15*pi*2/16)+ 2;
figure (2)
subplot(2,1,1)
stem(n,x)
ylabel('x(n)')
y=filter([
subplot(2,1,2)
stem(n,y)
ylabel('y(n)')
xlabel('n')
end
```

just not sure what to use in yfilter part. thx

Answer by LeBron on 11 Apr 2013

i hope someone replies thx