Value conversion & values outside expected range

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Spencer
Posts: 1
Joined: Thu May 02, 2019 12:33 am

Value conversion & values outside expected range

Post by Spencer »

Hi there,

Just hoping I can get some help understanding some of this stuff. I pulled .csv files into R and noticed values for each of the four channels, per band frequency. I am specifically looking at alpha. Am I correct in assuming these values are meant to fall between the expected -1.0 and 1.0 range? Is it normal for values to fall outside of that range? I have a mean alpha value for AF8 at -3.377.

I am also attempting to convert these values to the 0 to 100 display_value range, with the following formula you provided in another thread:

display_value = (value+1)/0.02

Is this the correct method? I've noticed some of my results have been far below the 0 minimum, and just thought I should make sure I was doing this correctly. Using the formula above, the text value of my mean alpha AF8 value would be -118.86.

EDIT: I think I got this all wrong, and I am supposed to convert the value from log10, based on a comment here from Ben Shapiro (result: 0.004). Any confirmation on this would be greatly appreciated!

With thanks,
Spencer
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James
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Posts: 1103
Joined: Wed Jan 02, 2013 9:06 pm

Re: Value conversion & values outside expected range

Post by James »

It's fine and normal for the values to be outside of -1:+1.
-3 sounds very low to me, but it's a log derivative and it can be pretty much anything.

You don't need to convert the values. I only do that because most lay people don't understand how to interpret a range of -1:+1, but with 0:100, they think of it like a percentage and it clicks... but if you do want to scale it, yes that's the formula I use for display.
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