The numericSequence class is a compact representation of a
numeric vector in an arithemetic sequence.
(numeric) the start of the sequence.
(numeric) the end of the sequence.
(numeric) the increment for the sequence.
(integer) the length of the sequence.
The numericSequence class extends the positionsNumeric class.
Valid numericSequence objects must contain a single non-NA number in
at least three of the four slots. If all four are present, the length
slot is ignored, and a warning message is generated when the sequence is used.
If length is present and not ignored, it must
be non-negative. (A zero-length sequence is equivalent to numeric(0).)
Otherwise, the sign of the by slot must agree with the sign of
(to - from) to have a valid sequence. In particular, if by is zero,
then to and from must be equal. The default sequence
(generated by calling numericSequence() or
new("numericSequence")) has length 0.
A numericSequence can be coerced to numeric or integer using as,
and regularly-spaced numbers can be coerced to numericSequence
using as. This fails if the input is not a regular arithmetic
sequence within a tolerance given by timeDateOptions("ts.eps").
Most operations on numericSequence objects (for example, mathematical functions,
arithmetic, comparison operators, or subscripting) work by first coercing to a numeric
vector, and therefore do not return numericSequence objects.
numericSequence function.