<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi Subbu,<div><br></div><div>To follow up on David's reply: when you use the ft_resampledata function, the data is also automatically low-passfiltered to avoid aliasing.</div><div>Highpass filtering is not necessary to avoid aliasing, but in general helps to make the data better behaved at the edges, which avoids ringing of the low-pass filter.</div><div><br></div><div><br></div><div><br></div><div>Best,</div><div><br></div><div>Jan-Mathijs</div><div><br><div><div>On Jan 11, 2013, at 4:36 AM, David Groppe wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div>You need to low-pass filter the data before downsaple to avoid aliasing.<br>The matlab function decimate.m can do this for you.<br> cheers,<br> -David<br><br>On Thu, Jan 10, 2013 at 3:22 PM, Narayan Iyer <<a href="mailto:eeguser@hotmail.com">eeguser@hotmail.com</a>> wrote:<br><blockquote type="cite">Hi<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">I have a question on EEG preprocessing. The sampling rate of my 64 channel<br></blockquote><blockquote type="cite">EEG data is 500 Hz and I would like to down-sample this to 256 Hz or 128 Hz.<br></blockquote><blockquote type="cite">My question is, i it advisable to low-pass filter the data first (70 Hz) and<br></blockquote><blockquote type="cite">then down-sample followed by high-pass filter (0.5 Hz) to avoid aliasing<br></blockquote><blockquote type="cite">effect or should I down-sample first and then band-pass filter the data<br></blockquote><blockquote type="cite">(0.5-70 Hz) ? Or does the sequence really matter ?<br></blockquote><blockquote type="cite">I am new to EEG data analysis so this question might be really basic, but<br></blockquote><blockquote type="cite">any help is highly appreciated!<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">Thanks<br></blockquote><blockquote type="cite">Subbu<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">_______________________________________________<br></blockquote><blockquote type="cite">fieldtrip mailing list<br></blockquote><blockquote type="cite"><a href="mailto:fieldtrip@donders.ru.nl">fieldtrip@donders.ru.nl</a><br></blockquote><blockquote type="cite"><a href="http://mailman.science.ru.nl/mailman/listinfo/fieldtrip">http://mailman.science.ru.nl/mailman/listinfo/fieldtrip</a><br></blockquote><br><br><br>-- <br>David Groppe, Ph.D.<br>Postdoctoral Researcher<br>North Shore LIJ Health System<br>New Hyde Park, New York<br><a href="http://www.cogsci.ucsd.edu/~dgroppe/">http://www.cogsci.ucsd.edu/~dgroppe/</a><br>_______________________________________________<br>fieldtrip mailing list<br>fieldtrip@donders.ru.nl<br>http://mailman.science.ru.nl/mailman/listinfo/fieldtrip<br></div></blockquote></div><br><div>
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>Jan-Mathijs Schoffelen, MD PhD </div><div><br></div><div>Donders Institute for Brain, Cognition and Behaviour, <br>Centre for Cognitive Neuroimaging,<br>Radboud University Nijmegen, The Netherlands</div><div><br></div><div>Max Planck Institute for Psycholinguistics,</div><div>Nijmegen, The Netherlands</div><div><br></div><div><a href="mailto:J.Schoffelen@donders.ru.nl">J.Schoffelen@donders.ru.nl</a></div><div>Telephone: +31-24-3614793</div></div></span></div></span></div></span></div></span></div></span></span>
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