<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=ISO-8859-15">
</head>
<body bgcolor="#ffffff" text="#000000">
<div class="moz-text-html" lang="x-western"> <font color="#000000">Hi
eeglab list gurus<br>
<br>
I have a problem that I really can't figure out on my own. I
have eeg data recorded from 64 electrodes + reference</font> <font
class="Apple-style-span" color="#000000"> (CPz). I find that
using different filters changes the rank of the matrix in ways I
would not have anticipated.</font><font color="#000000"><br>
<br>
First, I used a Butterworth highpass (.5Hz) and a Chebychew
lowpass (25Hz) filter </font> <font class="Apple-style-span"
color="#000000">on the raw data and then </font><font
color="#000000">reconstructed CPz </font><font
class="Apple-style-span" color="#000000">in the process of</font><font
color="#000000"> re-referenc</font><font
class="Apple-style-span" color="#000000">ing</font><font
color="#000000"> to average</font><font class="Apple-style-span"
color="#000000">, and then </font><font color="#000000">epoched</font><font
class="Apple-style-span" color="#000000"> the file</font><font
color="#000000"> resulting in a EEG.data(:,:,1) matrix with rank
65.<br>
When computing the ICA using runica() I get a warning: "fixing
rank computation inconsitency (65 vs 64) most likely because
running under Linux 64-bit Matlab".<br>
The server that I ran it on is indeed 64-bit, but it's a windows
server... the ICA creates 65 ICs, as </font><font
class="Apple-style-span" color="#000000">many </font><font
color="#000000">as there are Channels!<br>
<br>
Second, I used the eegfilt function (highpass: .5 / lowpass:25)
on the raw data and repeated the process as described above.
Now, after reconstructing and re-referencing EEG.data(:,:,1) has
a rank of 64.</font> <font color="#000000"><br>
When computing ICA i get the warning: "Data rank (64) is smaller
than the number of channels (65)"<br>
and sure enough ICA composes only 64 ICs!<br>
<br>
Does any one know why this is happening?</font> <font
color="#000000"><br>
<br>
Many thanks!</font> <font color="#000000"><br>
</font><font color="#000000"> <br>
Thomas</font> </div>
</body>
</html>