Seems to me that radius of 1 gives 7 voxels, e.g.: In [117]: radii = range(5)
In [118]: for radius in radii: .....: sp = Sphere(radius=radius) .....: size = len(sp((1,1,1))) .....: print "Radius %d size: %d" % (radius,size) .....: Radius 0 size: 1 Radius 1 size: 7 Radius 2 size: 33 Radius 3 size: 123 Radius 4 size: 257 Jonas ---- Jonas Kaplan, Ph.D. Research Assistant Professor Brain & Creativity Institute University of Southern California On Sep 10, 2012, at 8:39 AM, J.A. Etzel <[email protected]> wrote: > Your question touches on something I've been meaning to post about: how > exactly to shape a searchlight? As far as I know, there isn't a consensus. > > I posted images at http://mvpa.blogspot.com/2012/09/searchlight-shapes.html > showing one-voxel-radius surrounds containing 6, 18, and 26 voxels. (If you > know of others in use, let me know!) > > I'll leave it for the pyMVPA experts to say if a one-voxel radius searchlight > corresponds to 9 voxels; that doesn't sound right to me, either. > > Jo > > > On 9/9/2012 2:24 PM, Ping-Hui Chiu wrote: >> Dear PyMVPA experts, >> >> r=0, 1, 3 respectively correspond to 1, 9, 123 voxels in the following page: >> >> http://dev.pymvpa.org/examples/searchlight.html >> >> However, doesn't r=1 encompass 1 center+6 faces=7 voxels? >> Also, is there a formula for calculating the number of voxels given a >> specific radius? >> Finally, suppose a voxel=3*3*3mm, is it correct that r=3 covers up a >> neighborhood of (left 3*3mm + center 1*3mm + right 3*3mm)=21mm spherically? >> >> Thanks! >> Dale > > -- > Joset A. Etzel, Ph.D. > Research Analyst > Cognitive Control & Psychopathology Lab > Washington University in St. Louis > http://mvpa.blogspot.com/ > > _______________________________________________ > Pkg-ExpPsy-PyMVPA mailing list > [email protected] > http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/pkg-exppsy-pymvpa _______________________________________________ Pkg-ExpPsy-PyMVPA mailing list [email protected] http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/pkg-exppsy-pymvpa
