[FieldTrip] about detrend

[Yun Wen]

Hi, Alexander & Rodrigo. Thank you very much for your help. I collected my data with DC recordings (BioSemi system). I have seen some discussion on the DC offset:
http://sccn.ucsd.edu/pipermail/eeglablist/2014/008068.html
http://sccn.ucsd.edu/pipermail/eeglablist/2008/002229.html
http://sccn.ucsd.edu/pipermail/eeglablist/2010/003315.html
http://erpinfo.org/erplab/erplab-documentation/manual/Filtering.html

It seems to me that I'd better remove DC offset of continuous data before high-pass filter. Am I right?
Best,
Yun

From: fieldtrip-bounces at science.ru.nl [mailto:fieldtrip-bounces at science.ru.nl] On Behalf Of Alexander Nakhnikian
Sent: Friday, December 05, 2014 10:19 PM
To: FieldTrip discussion list
Subject: Re: [FieldTrip] about detrend

Hello Again,

I think there's an error in my response. I think removing the linear trend should also set the mean to zero already since the best fit line incorporates vertical offset.  Sorry about that.

A



On 12/5/14, 4:20 PM, Yun Wen wrote:
Hi all, I want to remove DC offset before applying the high-pass filter. I  was wondering if I can achieve that by putting cfg.detrend = 'yes' before cfg.hpfilter = 'yes', something like:

cfg = [];
cfg.dataset = filename_raweeg;
cfg.detrend = 'yes';
cfg.hpfilter = 'yes';
cfg.hpfiltord = 2; % Order of the filter = 2.
cfg.hpfreq = 0.1; % High-pass cutoff at 0.1 Hz;
[data] = ft_preprocessing (cfg);

Thank you in advance.

Best,
Yun






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