astro/

inertiatens.pro

top source inertiatens

Astro

result = inertiatens(pos, masses=masses, r2weight=r2weight)

Calculates the 2nd moment tensor (sometimes incorrectly referred to as the moment of inertia tensor) of a mass distribution specified by a list of particle positions.

Return value

The function returns a 3x3 symmetric array containing the 2nd moment of the mass distribution tensor, i.e. Result[i,j] is the sum over each particle k of MASSES[k] * Pos[k,i] * Pos[k,j].

Parameters

pos in: An Nx3 array specifying the 3d positions of the N particles that make up the mass distribution.

Keywords

masses in: An N-element vector of the mass of each point. If not specified, all masses are assumed to be unity.
r2weight in: If /R2WEIGHT is specified then particles are downweighted by a factor of 1/r^2 so that all particles have equal effect regardless of radius.

Examples

      Calculate the inertia tensor of 6 equal-mass points distributed on
      the vertices of a cube:

      xmasspos = [-1,-1,-1,-1,1,1,1,1]
      ymasspos = [-1,-1,1,1,-1,-1,1,1]
      zmasspos = [-1,1,-1,1,-1,1,-1,1]
      itens = INERTIATENS([[xmasspos],[ymasspos],[zmasspos]])

Author information

History:: Written by: Jeremy Bailin 10 June 2008 Public release in JBIU 22 July 2011 Bug fix for /R2WEIGHT to actually do something useful

File attributes

Modification date:	Fri Jul 22 11:40:27 2011
Lines:	69

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