How does filter function works?

2011 12 13
1 个回答
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Hi,
I used edit filter to see how does it work but I did not find any relative information. I used FIR filter filter(b,1,signal). I need to know how does it work.
Thankss

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回答（1 个）

Daniel Shub
Daniel Shub 2011-12-13

1 个投票

See this filter documentation
doc filter
as well as this question: http://www.mathworks.com/matlabcentral/answers/9900-use-filter-constants-to-hard-code-filter

6 个评论
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Jan
Jan 2011-12-13
I agree completely. +1
khatereh
khatereh 2011-12-20
Thanks for your answer but what is z ? I am designing a FIR filter so I don't have any a (a=1) but what is z?
Thanksss so much
Jan
Jan 2011-12-20
As explained in the documentation, z is the current status of the filter. The input z is the initial condition of the filter, the z in the output is the final condition. If you omit the input z it is set to the zero matrix.
You find the M-code for the filter command in the link Daniel has posted. There your can inspect what z does.
Daniel Shub
Daniel Shub 2011-12-20
@khatereh, it depends on what the context is. As Jan mention it could be the filter state. The term z^(-n) can also represent a delay.
khatereh
khatereh 2012-1-6
Thanks for your reply. I calculated coefficient b of low pass filter it is a FIR filter so the a is equal to 1. What should be the input value of z? if you look at the code the z gets updated each time and the final out put of the signal is related to that. I am confused. :(
Daniel Shub
Daniel Shub 2012-1-6
I am guessing you want to leave it out. The zi/zf input/outputs are most useful for when you are filtering in blocks. I believe that if you leave zi out, MATLAB assumes that the input has been zero for a very long time.

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khatereh
khatereh
2011-12-13

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