knotR (version 1.0-4)

overunder: Functionality for specifying overstrands and understrands

Description

Functionality for specifying overstrands and understrands

Usage

overunder(x)
overunder(x) <- value
mirror(x)
is.sensible(overunderobj,x)

Arguments

x

A knot object

value,overunderobj

A two-column integer matrix specifying the senses of the crossings in a knot

Author

Robin K. S. Hankin

Details

Function overunder() returns a two-column integer matrix with rows corresponding to crossing points. The first element of each row corresponds to the strand number of the overstrand and the second element corresponds to the understrand.

Function is.sensible() checks to see whether the overunder matrix is compatible with the knot path. For example, it checks to see whether each crossing has exactly one row, and that each row corresponds to a pair of strands that actually cross.

Function mirror() takes a knot and returns the knot with the senses of each crossing reversed; it is as though the knot is reflected in the plane of the projection.

See Also

knot

Examples

overunder(k4_1)

par(mfcol=c(1,2))
knotplot(k4_1,gap=80)
knotplot(mirror(k4_1),gap=80)

is.sensible(overunder(k6_1),k6_1)