sfsmisc (version 1.0-15)

seqXtend: Sequence Covering the Range of X, including X

Description

Produce a sequence of unique values (sorted increasingly), containing the initial set of values x. This can be useful for setting prediction e.g. ranges in nonparametric regression.

Usage

seqXtend(x, length., method = c("simple", "aim", "interpolate"),
        from = NULL, to = NULL)

Arguments

x

numeric vector.

length.

integer specifying approximately the desired length() of the result.

method

string specifying the method to be used. The default, "simple" uses seq(*, length.out = length.) where "aim" aims a bit better towards the desired final length, and

from, to

numbers to be passed to (the default method for) seq(), defaulting to the minimal and maximal x value, respectively.

Value

• numeric vector of increasing values, of approximate length length. (unless length. < length(unique(x)) in which case, the result is simply sort(unique(x))), containing the original values of x.

  From, r <- seqXtend(x, *), the original values are at indices ix <- match(x,r), i.e., identical(x, r[ix]).

See Also

seq; plotDS can make particularly good use of seqXtend()

Examples

a <- c(1,2,10,12)
seqXtend(a, 12)# --> simply 1:12
seqXtend(a, 12, "interp")# ditto
seqXtend(a, 12, "aim")# really worse
stopifnot(all.equal(seqXtend(a, 12, "interp"), 1:12))

## for a "general" x, however, "aim" aims better than default
x <- c(1.2, 2.4, 4.6, 9.9)
length(print(seqXtend(x, 12)))        # 14
length(print(seqXtend(x, 12, "aim"))) # 12
length(print(seqXtend(x, 12, "int"))) # 12

## "interpolate" is really nice:
xt <- seqXtend(x, 100, "interp")
plot(xt, main="seqXtend(*, 100, "interpol")")
points(match(x,xt), x, col = 2, pch = 20)
# .... you don't even see that it's not equidistant
# whereas the cheap method shows ...
xt2 <- seqXtend(x, 100)
plot(xt2, col="blue")
points(match(x,xt2), x, col = 2, pch = 20)