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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bob cox
February 16, 2003 10:48AM
Any "higher order" interpolation or filtering scheme (which includes the methods used in 3dFourier) has the potential for producing values that exceed the min..max range of the data. What is probably happening in your data is that values near the edge of the brain have very low intensity (min near 0), so going below that range is obvious. In the center of the brain, there are undoubtedly values below the local min value, but those aren't so obvious (372 doesn't look so different than 400, for example).

If you wish to clip off these negative annoyances, you can do so with a 3dcalc command of the form

3dcalc -a zork+orig -expr 'step(a)*a' -prefix zork_clipped

bob cox
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Subject Author Posted

Negative Values

Lukas Pezawas February 15, 2003 10:08PM

Re: Negative Values

bob cox February 16, 2003 10:48AM

Thanks!

Lukas Pezawas February 16, 2003 03:43PM