Content-type: text/html Manpage of sfanis

sfanis

Section: User Commands (1)
Index Return to Main Contents

NAME

sfanis - Computes an index of anisotropy of spherical functions.

SYNOPSIS

sfanis -inputmodel <sh|rbf|maxent> [options]

DESCRIPTION

Computes the anisotropy of any input spherical function. The anisotropy of a function f is sqrt(int(f(x) - F)^2/int(f^2(x))) where F = int(f(x)) and the integrals are all over the unit sphere. For functions represented as spherical harmonic series, the calculation uses an analytic expression and is very fast to compute. For other representations, the program approximates the integrals by summing over a set of around 8000 points evenly distributed on the sphere. To decrease computation time, the size of the point set can be reduced using the -pointset option.

EXAMPLES

Here are some examples using synthetic data.

Create a synthetic data set:

datasynth -testfunc 3 -snr 16 -voxels 4 -schemefile test/bmx7.scheme > T3_BMX7.Bfloat

Fit the spherical harmonics with maximum order 2 and compute the anisotropy:

shfit -order 2 -schemefile test/bmx7.scheme < T3_BMX7.Bfloat | sfanis -inputmodel sh -order 2 | double2txt

2.588603E-01
2.597550E-01
2.537685E-01
2.980303E-01

Try with maximum order 4: shfit -order 4 -schemefile test/bmx7.scheme < T3_BMX7.Bfloat | sfanis -inputmodel sh -order 4 | double2txt

2.983556E-01
3.064308E-01
2.876707E-01
3.385700E-01

Repeat using PASMRI: mesd -filter PAS 1.4 -schemefile test/bmx7.scheme < T3_BMX7.Bfloat | sfanis -inputmodel maxent -filter PAS 1.4 -mepointset 54 | double2txt

9.936683E-01
9.938231E-01
9.579966E-01
9.970216E-01

Repeat using QBALL: qballmx -schemefile test/bmx7.scheme > /tmp/bmx7_QBALLMX.Bdouble linrecon T3_BMX7.Bfloat test/bmx7.scheme /tmp/bmx7_QBALLMX.Bdouble -normalize | sfanis -inputmodel rbf -rbfpointset 246 -rbfsigma 0.2617993877991494 -schemefile test/bmx7.scheme | double2txt 1.049307E-01 1.180261E-01 1.087973E-01 1.186283E-01

And spherical harmonic q-ball qballmx -schemefile test/bmx7.scheme -basistype sh -order 4 > /tmp/bmx7_QBALLMX.Bdouble linrecon T3_BMX7.Bfloat test/bmx7.scheme /tmp/bmx7_QBALLMX.Bdouble -normalize | sfanis -inputmodel sh -order 4 -schemefile test/bmx7.scheme | double2txt 1.204591E-01 1.364328E-01 1.265906E-01 1.379158E-01

OPTIONS

-inputmodel <sh|rbf|maxent|dt>

Tells the program what type of functions are input. Currently supported options are:

sh - Spherical harmonic series. (Must specify -order.)

maxent - Maximum entropy representations output by mesd. (Must specify -filter and -mepointset.)

rbf - Sums of radial basis functions. (Must specify rbf parameters, eg -rbfsigma, and -rbfpointset.)

-pointset <|1|2|3|4|5|6|7>

Choose the point set used for the numerical integration. The point sets have sizes:

0 - 1082
1 - 1922
2 - 4322
3 - 8672
4 - 15872
5 - 32672
6 - 72032
7 - 78032

The default is point set 3.

BUGS

AUTHOR

Danny Alexander <camino@cs.ucl.ac.uk>

This document was created by man2html, using the manual pages.
Time: 02:07:11 GMT, December 04, 2017

Sfanis