quadrupole: Quadrupole tensor
In cooltools: Practical Tools for Scientific Computation and Visualisation

quadrupole

R Documentation

Quadrupole tensor

Computes the trace-free mass quadrupole tensor of a set of point masses in arbitrary dimensions,

\mathbf{Q} = \sum_i m_i \left( d\,\mathbf{x}_i\mathbf{x}_i^\mathrm{T} - |\mathbf{x}_i|^2\mathbf{I} \right),

where d is the dimensionality of the points and \mathbf{I} is the d\times d identity matrix.

quadrupole(x, m = 1)

`x`	Numeric vector or matrix. If a matrix is supplied, each row is interpreted as a point.
`m`	Numeric scalar or vector of point masses. If a scalar is supplied, the same mass is assigned to every point.

A symmetric d\times d matrix containing the trace-free quadrupole tensor.