AFNI Message Board

Dear AFNI users-

We are very pleased to announce that the new AFNI Message Board framework is up! Please join us at:

https://discuss.afni.nimh.nih.gov

Existing user accounts have been migrated, so returning users can login by requesting a password reset. New users can create accounts, as well, through a standard account creation process. Please note that these setup emails might initially go to spam folders (esp. for NIH users!), so please check those locations in the beginning.

The current Message Board discussion threads have been migrated to the new framework. The current Message Board will remain visible, but read-only, for a little while.

Sincerely, AFNI HQ

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rick reynolds
December 08, 2016 12:52PM
Hi Prerona,

This should not affect the significance of any results
(since it is constant scalar across all subjects, unless
it is unbalanced, like A+B+C-D-E), but it is often nice
to make contrasts of unit weight in the positive and
negative directions.

So for a simple A-B contrast -expr a-b is good. But
for a contrast of ((A-B) - (C-D)), it might be better to
divide by 2, since this ends up as (A+D) - (B+C), and
each has a weight of 2. So for that, consider
-expr '(a+d)/2-(b+c)/2'.

- rick
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Subject Author Posted

correct expression for 3dCalc

prerona December 07, 2016 03:23PM

Re: correct expression for 3dCalc

rick reynolds December 08, 2016 12:52PM

Re: correct expression for 3dCalc

prerona December 08, 2016 08:33PM