butterworth filter

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Sam Hamie
Sam Hamie on 19 Mar 2012
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'.
  1 Comment
Honglei Chen
Honglei Chen on 19 Mar 2012
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

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Answers (3)

Wayne King
Wayne King on 19 Mar 2012
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?
  1 Comment
Sam Hamie
Sam Hamie on 20 Mar 2012
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

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Wayne King
Wayne King on 20 Mar 2012
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.
  2 Comments
Sam Hamie
Sam Hamie on 20 Mar 2012
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
Honglei Chen on 20 Mar 2012
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).

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Daniel Shub
Daniel Shub on 20 Mar 2012
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...

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