[Eeglablist] Channel Scroll Data

Tarik S Bel-Bahar tarikbelbahar at gmail.com
Mon Aug 14 11:13:15 PDT 2017

Hello Cassandra, some brief notes below:

1. Changing the scale should change change all values equally.

2. I'm not sure, but values are most likely in microvolts, please google
past eeglablist messages on this topic (what are the values in eegplot)
I don't think that eeglab changes the values of data that comes in, but it
may depend on the format of the data that is imported, the way that the
data was exported from the EEG recording software, and steps that happen
upon importation.
Please review the documentation on importing the kind of data file you
Your best bet is to examine the values in the data directly. Check your
original values for a specific time in your original files, and then try to
confirm that they are  the same when viewing them in several different ways
(outside of eegplot).

3. check to make sure  that you are/are not norming in the eegplot (e.g.,
the Norm button). This can also impact the values in the plot.
I believe that Norm works on just the time periods currently shown in

4. All channels should be in the same scale already, make sure you are
"seeing all channels" at once.

5. It's possible that eegplot is modifying the values for each window of
time it is showing you. Your best best to estimate the real values is to
look into EEG.data and confirm/disconfirm from there. You can also use
normal matlab plotting of EEG.data to get a sense of differences that may
be occuring with eegplot.

6. You may want to send pictures and a sample file if you have further

On Fri, Aug 11, 2017 at 1:27 PM, Cassandra Nguyen <casnguyen at ucdavis.edu>

> Hello,
> I am using the Channel Data Scroll plot in EEGLAB and I have some
> questions about the plot.
> Are the units on the right side of the plot (e.g., Scale 100) in
> microvolts since our data was collected in microvolts?
> What do the "Value" numbers mean and why do they change when the scale is
> changed? When I go to find the value of the peak of a channel, the number
> sometimes is lower than the value of a clearly lower peak from a different
> channel. For example, when finding the min/max values of a blink, channel
> E128 will have a value of 117.8441 and channel E127 will have value of
> -34.441 even though channel E128 clearly has a much lower minimum than
> E127. Is there a way to get all of the channels that I wish to look at to
> be on the same scale?
> Thank you,
> Cassandra Nguyen
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