<div dir="ltr"><div>I just realized I accidentally forgot to do reply all and the subsequent responses weren't posted on the mailing list, so I'm forwarding it back on for anyone else who was following. Sorry!<br><br>
</div><div><div class="gmail_quote">---------- Forwarded message ----------<br>From: <b class="gmail_sendername">Max Cantor</b> <span dir="ltr"><<a href="mailto:mcantor@umich.edu">mcantor@umich.edu</a>></span><br>Date: Thu, Jan 30, 2014 at 9:24 AM<br>
Subject: Re: [FieldTrip] Problem with ICA using data exported via Brainvision analyser<br>To: Hwee Ling Lee <<a href="mailto:hweeling.lee@gmail.com">hweeling.lee@gmail.com</a>><br><br><br><div dir="ltr"><div>I'm not sure I understand what you mean by not being able to find the data that corresponds to the reference channel. For your call to ft_componentanalysis, for cfg.channel, if you set it to {'all', '-refchan'}, where refchan stands for whatever your reference channel is called, that should remove the reference channel from ICA. If you're issue is what I think it is, this tutorial should reiterate what I'm talking about: <br>
<br><a href="http://fieldtrip.fcdonders.nl/faq/why_does_my_ica_output_contain_complex_numbers" target="_blank">http://fieldtrip.fcdonders.nl/faq/why_does_my_ica_output_contain_complex_numbers</a><br><br></div>Sorry if I'm misunderstanding the problem you're having, but hopefully this clarifies things.<br>
</div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, Jan 30, 2014 at 8:35 AM, Hwee Ling Lee <span dir="ltr"><<a href="mailto:hweeling.lee@gmail.com" target="_blank">hweeling.lee@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><p dir="ltr">Dear Max,<br>
Thanks for taking your time to explain this. I would like to try your suggestion, but the problem is that i don't know which channel i should remove from my data since i can't find the data that corresponds to the reference channel. <br>
The funny thing for me at least is that this problem does not occur when i use the raw data that has not been exported by brainvision analyser. I'll try to look at the archives regarding this.<br>
Thanks again.<br>
Cheers,<br>
Hweeling<br>
</p><div><div>
<div class="gmail_quote">On 30 Jan 2014 13:54, "Max Cantor" <<a href="mailto:mcantor@umich.edu" target="_blank">mcantor@umich.edu</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">Hm, did you try it? I had a similar issue awhile back and that solved it for me. Let me see if I can explain this correctly: I think the fact that there is no data from the reference channel is exactly the problem. ICA is performing a transform on the data, 'rotating' the data from channel space to component space, based on rank. If there is no data in any of the channels, you're asking ICA to transform the data into more components than effectively there are channels; in other words the dimensions in the 'rotation' of the data (if you think of the transform like a geometric rotation) are off. Hopefully that explanation makes sense, or somebody else can explain it more adequately. I think somewhere in the archives there was a long thread about ICA where I and a few other people ask about this issue, so that may help as well.</div>
<div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, Jan 30, 2014 at 5:58 AM, Hwee Ling Lee <span dir="ltr"><<a href="mailto:hweeling.lee@gmail.com" target="_blank">hweeling.lee@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi Max,<div><br></div><div>Thanks for your suggestion. However, I checked the data, there was no data from the reference channel, so I doubt this is the problem for the rank issue.</div>
<div><br></div><div>Cheers,</div>
<div>Hweeling</div><div><br></div></div><div class="gmail_extra"><div><div><br><br><div class="gmail_quote">On 29 January 2014 15:31, Max Cantor <span dir="ltr"><<a href="mailto:mcantor@umich.edu" target="_blank">mcantor@umich.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi Hwee,<div><br></div><div>It may be your reference channel. Try removing your reference channel from ICA and it should resolve the rank issue.</div>
<div><br></div><div>Max Cantor</div><div>Research Assistant</div>
<div>Computational Neurolinguistics Lab</div><div>University of Michigan</div></div><div class="gmail_extra"><br><br><div class="gmail_quote"><div><div>On Wed, Jan 29, 2014 at 8:57 AM, Hwee Ling Lee <span dir="ltr"><<a href="mailto:hweeling.lee@gmail.com" target="_blank">hweeling.lee@gmail.com</a>></span> wrote:<br>
</div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div><div dir="ltr"><div dir="ltr"><div>Dear all,</div><div><br></div><div>Whenever I export my EEG data using Brainvision analyser, I get problems with running ICA on Fieldtrip. The data has a different rank, although I specify to compute ICA using all channels.</div>
<div><br></div><div>However, when I use the raw EEG data collected from Brainvision recorder, I do not get this problem.</div><div><br></div><div>Does anyone know why and how to resolve this issue?</div><div><br></div><div>
My purpose of using Brainvision analyser is to downsample the EEG raw data before further analyses.</div><div><br></div><div>Thanks.</div><div><br></div><div>Best regards,</div><div>Hweeling</div><div><br></div></div>
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</blockquote></div><br><br clear="all"><div><br></div></div></div>-- <br><div dir="ltr">=================================================<br>Dr. rer. nat. Lee, Hwee Ling<br>Postdoc<br>German Center for Neurodegenerative Diseases (DZNE) Bonn<br>
<br>Email 1: hwee-ling.lee<at><a href="http://dzne.de" target="_blank">dzne.de</a><br>Email 2: hweeling.lee<at><a href="http://gmail.com" target="_blank">gmail.com</a><div><br></div><div><a href="https://sites.google.com/site/hweelinglee/home" target="_blank">https://sites.google.com/site/hweelinglee/home</a><br>
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