[b,a] = butter(4, 1000/2000,'low');freqz(b,a,128,4000)hold on

[b,a] = butter(5, 1000/2000,'low');freqz(b,a,128,4000)hold on

[b,a] = butter(6, 1000/2000,'low');freqz(b,a,128,4000)hold on

[b,a] = butter(7, 1000/2000,'low');freqz(b,a,128,4000)hold on

[b,a] = butter(8, 1000/2000,'low');freqz(b,a,128,4000)hold on

[b,a] = butter(9, 1000/2000,'low');freqz(b,a,128,4000)hold on

0 200 400 600 800 1000 1200 1400 1600 1800 2000-800

-600

-400

-200

0

Frequency (Hz)

Pha

se (

degr

ees)

0 200 400 600 800 1000 1200 1400 1600 1800 2000-400

-300

-200

-100

0

Frequency (Hz)

Mag

nitu

de (

dB)

[b,a] = butter(4, 1000/2000,'high');freqz(b,a,128,4000)hold on

[b,a] = butter(5, 1000/2000,'high');freqz(b,a,128,4000)hold on

[b,a] = butter(6, 1000/2000,'high');freqz(b,a,128,4000)hold on

[b,a] = butter(7, 1000/2000,'high');freqz(b,a,128,4000)hold on

[b,a] = butter(8, 1000/2000,'high');freqz(b,a,128,4000)hold on

[b,a] = butter(9, 1000/2000,'high');freqz(b,a,128,4000)hold on

0 200 400 600 800 1000 1200 1400 1600 1800 2000-1000

-500

0

500

Frequency (Hz)

Pha

se (

degr

ees)

0 200 400 600 800 1000 1200 1400 1600 1800 2000-400

-300

-200

-100

0

Frequency (Hz)

Mag

nitu

de (

dB)

[b,a] = butter(4, [1000 3000] /4000,'bandpass');freqz(b,a,128,8000)hold on

[b,a] = butter(5, [1000 3000]/4000,'bandpass');freqz(b,a,128,8000)hold on

[b,a] = butter(6, [1000 3000]/4000,'bandpass');freqz(b,a,128,8000)hold on

[b,a] = butter(7, [1000 3000]/4000,'bandpass');freqz(b,a,128,8000)hold on

[b,a] = butter(8, [1000 3000]/4000,'bandpass');freqz(b,a,128,8000)hold on

[b,a] = butter(9, [1000 3000]/4000,'bandpass');freqz(b,a,128,8000)hold on

0 500 1000 1500 2000 2500 3000 3500 4000-2000

-1000

0

1000

Frequency (Hz)

Pha

se (

degr

ees)

0 500 1000 1500 2000 2500 3000 3500 4000-300

-200

-100

0

Frequency (Hz)

Mag

nitu

de (

dB)

[b,a] = butter(4, [1000 3000] /4000,'stop');freqz(b,a,128,8000)hold on

[b,a] = butter(5, [1000 3000]/4000,'stop');freqz(b,a,128,8000)hold on

[b,a] = butter(6, [1000 3000]/4000,'stop');freqz(b,a,128,8000)hold on

[b,a] = butter(7, [1000 3000]/4000,'stop');freqz(b,a,128,8000)hold on

[b,a] = butter(8, [1000 3000]/4000,'stop');freqz(b,a,128,8000)hold on

[b,a] = butter(9, [1000 3000]/4000,'stop');freqz(b,a,128,8000)hold on

0 500 1000 1500 2000 2500 3000 3500 4000-1500

-1000

-500

0

Frequency (Hz)

Pha

se (

degr

ees)

0 500 1000 1500 2000 2500 3000 3500 4000-1000

-500

0

500

Frequency (Hz)

Mag

nitu

de (

dB)