Uncertainty class

[willat343]

There is demand for an "uncertainty" or "noise characteristics" class that catpures sigma/sigmas/variance/variances/covariance/precision/stiffness. The values can be precomputed and requires certain criteria (e.g. for stiffness we require covariance to be positive-definite unless we compute a pseudo-inverse).

This class can contain the functionality that currently exists in the stiffness and covariance files.

Currently the create of stiffness/covariance matrices from json is managed in sensorbox. Either:

• sensorbox should be able to create instances of this uncertainty class from json, or
• mathbox should inherit this functionality (adding a json dependency)
• or all the json functionality should move to another package like convert

[willat343]

A similar concept can be applied to an UncertaintyDensity class, generalising the current CovarianceDensity and providing other density functions (e.g. StiffnessDensity)