
From:  Doug Stewart 
Subject:  Re: data smoothing 
Date:  Wed, 19 Jan 2011 15:10:00 0500 
Hi Doug,I'm only interested in data after time 0.DominikOn Wed, Jan 19, 2011 at 5:31 PM, Doug Stewart <address@hidden> wrote:
On Wed, Jan 19, 2011 at 11:59 AM, mimi <address@hidden> wrote:
Hi,
My data was truncated to 8bits and needs some smoothing. Can anyone help
me with this?
What is the best approach here?
I have attached csv file.
thanks,
m
http://octave.1599824.n4.nabble.com/file/n3225426/test200ms.csv
test200ms.csv
Are you interested in the data before time zero or after?
a=load ("test200ms.csv");
b=a(:,1);
c=a(:,2);
s=900;
q=s+200;
figure(1)
plot(b(s:q),c(s:q))
figure (2)
w=fft(c(100:10000));
plot(abs(w))
figure(3)
cc=c(1000:10000);
[n,d]=butter(5,.3)
y=filter(n,d,cc);
plot(y(100:2900))
that is what I put together to try my ideas.
What I did was
1) look at the FFT (fast fourier transforme) of your data to see approximately what frequency your data was.
2) made a low pass butterworth filter so I can get rid of the high frequencies
3) filter the data after time zero cc is approximately after time zero you will do it more accurately than me.
4) figure 3 is the results
in the line [n,d]=butter(5,.3) the 5 is the order of the filter and the .3 is the cutoff frequency you should play with these to get the smoothness you want.
try the order from 2 to 8 and try the corner frequency from .1 to .9
Doug
PS I know the code is not the best  just a quick hack
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