# Spsk2mat.m

Converts span and skew representation of a 3x3 interaction tensor into the corresponding matrix.

## Syntax

    M=axrh2mat(iso,ax,rh,alp,bet,gam)


## Description

Isotropic part, span, and skew are often seen in the literature. It is not a good way of reporting an interaction tensor (the original matrix is best), but it is still being used.

## Arguments

       iso  - isotropic part of the interaction, defined as
(xx+yy+zz)/3 in terms of eigenvaues

sp  - interaction span, defined as the difference
between the largest and the smallest eigenvalue

sk  - interaction skew, defined as 3*(yy-iso)/sp
where yy is the middle eigenvalue

alp  - alpha Euler angle in radians

bet  - beta Euler angle in radians

gam  - gamma Euler angle in radians


## Outputs

    M  - 3x3 matrix


## Notes

The reverse transformation (from matrix into span, skew, and angles) is ill-defined.