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Thread Subject:
Smoothing of Data

Subject: Smoothing of Data

From: Talha

Date: 17 Jun, 2011 06:45:21

Message: 1 of 4

hi,
   i have ECG data and it contain as much 12000 data samples or plot points. Now whenever i plot the data i got the desired waveform with peaks touching around 2000 but at lower level i have noise riding the data or jitter kind of waveform or zig-zags at lower data values. I want to smooth it or remove the zig-zags present in the waveform.
 
    Is there a way i can accomplish it??
                       
                       Thanks.

Subject: Smoothing of Data

From: Rune Allnor

Date: 17 Jun, 2011 07:20:33

Message: 2 of 4

On Jun 17, 8:45 am, "Talha " <talha_a...@yahoo.com> wrote:
> hi,
>    i have ECG data and it contain as much 12000 data samples or plot points. Now whenever i plot the data i got the desired waveform with peaks touching around 2000 but at lower level i have noise riding the data or jitter kind of waveform or zig-zags at lower data values. I want to smooth it or remove the zig-zags present in the waveform.
>
>     Is there a way i can accomplish it??

Yes, but at some cost.

To get the extreme cases first:

1) You can leave the data as-is, after which all the noise etc are
   are in place, but where the desired signalis intact.
2) You can multiply each sample in the data sequence by 0, after
   which all noise is gone, but so is the desired signal.

Of course, the ideal result is that all the noise is gone while
all the desired signal is left.

This can not be achieved.

The best you can do, is to set up a spec that states

1) What distorsions to the desired signal are acceptable
2) What distorsions to the desired signal are untolerable
3) What properties of the noise are acceptable
4) What properties of the noise are untolerable

Only after you have come up with this kind of spec does
it make sense to start discussing methods for processing
the data.

Rune

Subject: Smoothing of Data

From: Krishna Kumar

Date: 17 Jun, 2011 10:46:04

Message: 3 of 4

"Talha " <talha_away@yahoo.com> wrote in message <itet61$cf1$1@newscl01ah.mathworks.com>...
> hi,
> i have ECG data and it contain as much 12000 data samples or plot points. Now whenever i plot the data i got the desired waveform with peaks touching around 2000 but at lower level i have noise riding the data or jitter kind of waveform or zig-zags at lower data values. I want to smooth it or remove the zig-zags present in the waveform.
>
> Is there a way i can accomplish it??
>
> Thanks.
Hi Talha,
I m not an expert in your domain. But I hope using Principal component analysis based
reconstruction approach may help your case. If you are interested in that
just google - pca for smoothing data or something like that. I hope I am right
hth,
Krishna

Subject: Smoothing of Data

From: ImageAnalyst

Date: 17 Jun, 2011 13:06:46

Message: 4 of 4

Talha
There are lots of ways to clean up ECG signals. I'm sure there are
many which are very specially designed for the special shape of the
ECG signal. You can find some of them here:
http://iris.usc.edu/Vision-Notes/bibliography/medical888.html#Heart%20Analysis,%20ECG,%20Electrocardiogram,%20Other%20Electrical%20Signals

In addition, there are some ECG files in the File Exchange:
http://www.mathworks.com/matlabcentral/fileexchange/?term=ECG

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