cube() returns an eight-by-eight conductancematrix for a skeleton
cube of 12 resistors. Each row/column corresponds to one of the 8
vertices that are the electrical nodes of the compound resistor. In one orientation, node 1 has position 000, node 2 position 001, node 3
position 101, node 4 position 100, node 5 position 010, node 6 position
011, node 7 position 111, and node 8 position 110.
To do a Wheatstone bridge, use tetrahedron() with one of the
resistances Inf.
In cube(), x is a vector of twelve elements (a scalar
argument is interpreted as the resistance of each resistor)
representing the twelve resistances of a skeleton cube. In the
orientation described below, the elements of x correspond to
$R_{12}$, $R_{14}$, $R_{15}$,
$R_{23}$, $R_{26}$, $R_{34}$,
$R_{37}$, $R_{48}$, $R_{56}$,
$R_{58}$, $R_{67}$, $R_{78}$ (here
$R_{ij}$ is the resistancd between node $i$ and
$j$). The pattern is general: edges are ordered first by the
row number $i$, then column number $j$.
In octahedron(), x is a vector of twelve elements (a
scalar argument is interpreted as the resistance of each resistor)
representing the twelve resistances of a skeleton octahedron. If node 1
is top and node 6 is bottom, the elements of x
correspond to
$R_{12}$, $R_{13}$, $R_{14}$,
$R_{15}$, $R_{23}$, $R_{25}$,
$R_{26}$, $R_{34}$, $R_{36}$,
$R_{45}$, $R_{46}$, $R_{56}$.