butterworth filter

I made the simple code for butterworth but i keep getting this error! Butter is not defined! can someone help?

>> order =1; >> sampling_freq=1000; >> cut_off_freq=10; >> [butter_b,butter_a]=butter(order, cut_off_freq/(sampling_freq)/2); ??? Undefined function or method 'butter' for input arguments of type 'double'.

[Honglei Chen]

Please don't post the same question twice. If necessary, you can always update your original question. I've answered this in your original thread

http://www.mathworks.com/matlabcentral/answers/32748-butterworth-filter

Answer 1

[Wayne King]

Hi Sam, do you have the Signal Processing Toolbox installed?

if you enter

>>ver

do you see an entry for Signal Processing Toolbox?

If you enter:

   license('test','signal_toolbox')

Do you get a 1?

[Sam Hamie]

Hello Wayne

Actually I dont have signal processing toolbox installed. and my >> license('test','signal_toolbox')

ans = 0

Please let me know where to get the signal processing toolbox?

I appreciate your help.

Thanks

sam

Answer 2

[Wayne King]

Hi Sam, You must contact MathWorks for licensing a new toolbox in your installation. And please do follow Honglei's good advice about double posting.

[Sam Hamie]

hello wayne,

is there a way were I can use any filter to clean/smooth my graph? My graph is only a bunch of data on X & Y axis!

It has to be a way were I can bypass the Signal Processing Toolbox!

thanks,

sam

[Honglei Chen]

If you just want to smooth the data, you can do a moving average, e.g., h = 0.25*ones(4,1) produces a 4-points moving average filter and you can filter your data x using conv(h,x).

Answer 3

[Daniel Shub]

Depending on how many filters you need and their orders, you may be able to calculate the coefficients by hand. You will probably need the signal processing toolbox to do anything useful with the coefficients...