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Data filtering or smoothing?

Data filtering or smoothing?

Data filtering or smoothing?

(OP)
Hi all,

Does anybody know about data smoothing or filtering?
I'm working on data processing. The experimental data has a lot of noise on it so I need to remove the data.
I'm studying about filtering with FFT and trying to program a subroutine in Fotran. It is extremely tough to understand and program it.
So if anybody has an experience with programing a filtering, please help me out.

Thank you very much in advance,

Will

RE: Data filtering or smoothing?

(OP)
Thank you IRstuff.
If you don't mind, could you talk to me specifically?
Actually, I don't know what and how to use.
I have spent almost a week on this. I don't have any progress. Please help me out.

Thanks again.

RE: Data filtering or smoothing?

(OP)
No, it is not at all.
I'm building my own program to process experiment data.
It is pressure data having a lot of noise. So I want to remove the noise.
I'm studying FFT digital filtering over and over, but it is difficult to understand. Also, I don't know whether the digital filtering is the best way to remove noise or not.
If you can help me out, I really appreciate it.
Please help me.

Thank you.

RE: Data filtering or smoothing?

>  Perhaps you should start with a better pressure sensor
>  How do you know it's really noise?
>  What is the actual behavior of the data, i.e., constant, varying, etc?
>  FFT filter is not that simple because most data is not periodic, so windowing effects can alter your data
>  The type of filtering depends on what your data looks like

TTFN

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RE: Data filtering or smoothing?

(OP)
Thank you for your comments.
The pressure data was measured in a combustion engine cylinder.
It is change with time and crank angle. The data shows the pressure trend, but it's noisy. So I want to remove the noise. Otherwise, I get unreasonable calculation result based on the measured pressure data.
If you have better idea, could you recommend me what to do?
I thank you very much for your time.  

RE: Data filtering or smoothing?

You should build in the butterworth filter (24dB) not FFT-filter.

RE: Data filtering or smoothing?

Ostensibly, a Butterworth filter has a Fourier transform.

> How many samples do you have relative to the features of interest, or equivalently, how many samples do you have along this "trend?"  Fewer samples is problematic; more samples allows more flexibility in determining the optimum course of action.

> How much distortion are you willing to tolerate?

TTFN

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