a two-column matrix of end-points, with column 1 defining the lower
end of each interval and column 2 the upper end (inclusive on both ends);
or a numeric vector of zero-width intervals.
VALUE:
object of class
shingle: the numeric vector,
x , with an
intervals
attribute as a two-column matrix of intervals.
levels(x)
will return the
intervals attribute if
x is a shingle.
is.shingle returns
TRUE if
x is a shingle object,
FALSE otherwise.
as.shingle returns
x, if
x is a shingle,
shingle(x) otherwise.