# [Eeglablist] How do I measure ratio of EEG frequency band for a few electrodes in decibels?

Tarik S Bel-Bahar tarikbelbahar at gmail.com
Mon Aug 28 11:05:30 PDT 2017

```Hello Goh, a few notes below:

*********************************************************

Your best bet is to use a calculation based on a published recent papers in
high-quality journals.
Such ratios are also used in QEEG research, so also look in that literature.

If you have questions about basic theory/maths of frequency computations,
see Mike X. Cohen's excellent book, and related website materials. I may be
wrong, but I don't frequency computations in eeglab lead to results in
microvolts. Please review function documentation, and labels on axes of

See also past eeglablist posts on this topic by googling eeglablist + your
topic.

On Sun, Aug 27, 2017 at 11:42 AM, goh victor <saltnote at hotmail.com> wrote:

> I wanted to calculate the ratio of Theta/Beta in decibels for a couple of
> electrodes in AF3 AF4 and Cz
>
> I was able to get these in microvolts, but would like to convert them to
> decibels but am unsure what is the appropriate way to do so.
>
> For instance, should I convert it like:
>
>     ratio1 = 10Log((Theta(AF3) + Theta(AF4) + Theta(Cz))/(Beta(AF3) +
> Beta(AF4) + Beta(Cz)))
>
> or
>
>     ratio2 = 10Log(Theta(AF3)/Beta(AF3)) + 10Log(Theta(AF4)/Beta(AF4)) +
> 10Log(Theta(Cz)/Beta(Cz))
>
> <http://aka.ms/weboutlook>
>
> _______________________________________________
> Eeglablist page: http://sccn.ucsd.edu/eeglab/eeglabmail.html
> To unsubscribe, send an empty email to eeglablist-unsubscribe at sccn.
> ucsd.edu
> For digest mode, send an email with the subject "set digest mime" to
> eeglablist-request at sccn.ucsd.edu
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sccn.ucsd.edu/pipermail/eeglablist/attachments/20170828/9d74a0b6/attachment.html>
```