Re: need help filtering a signal

[Shengchao Li]

their is frequency associated with the fft result. It depends on what is
your sampling rate. You need to give us
1. the sampling rate (how many samples per second)
2. how long your trunk of data is
3. the frequency range of your signal

before we can find out the frequency in your fft output.

shengchao

On Fri, 7 Dec 2001, Philipp Schwaha wrote:

> hi!
> 
> what i need to do is fiter a signal to remove noise. what i wanted to try 
> first was a fft then cut all frequencies except the the important ones (e.g 
> 100Hz, 200Hz ...), but when i did the fft i did not know how to do this, 
> since there are no frequencies associated with the values the function fft 
> returns. 
> this is the first time i try to do something using an fft.
> then i discovered the function fftfilter, but i could not make it produce the 
> results i wanted.
> 
> how can i remove all frequencies from a certain signal, except a few selected 
> ones?
> 
> thanks
> philipp
> 
> 
> 
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