sfsmisc: seqXtend – R documentation

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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 `"interpolate"` interpolates evenly inside* each interval (x[i], x[i+1]) in a way to make all the new intervalls of approximately the same length.
`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]).

Note

method = "interpolate" typically gives the best results. Calling roundfixS, it also need more computational resources than the other methods.

Author(s)

Martin Maechler

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)

## with "Date" objects
Drng <- as.Date(c("2007-11-10", "2012-07-12"))
(px <- pretty(Drng, n = 16)) # say, for the main labels
## say, a finer grid, for ticks -- should be almost equidistant
n3 <- 3*length(px)
summary(as.numeric(diff(seqXtend(px, n3))))        # wildly varying
summary(as.numeric(diff(seqXtend(px, n3, "aim")))) #   (ditto)
summary(as.numeric(diff(seqXtend(px, n3, "int")))) # around 30

sfsmisc

Utilities from 'Seminar fuer Statistik' ETH Zurich

v1.1-11

GPL (>= 2)

Authors

Martin Maechler [aut, cre] (<https://orcid.org/0000-0002-8685-9910>), Werner Stahel [ctb] (Functions: compresid2way(), f.robftest(), last(), p.scales(), p.dnorm()), Andreas Ruckstuhl [ctb] (Functions: p.arrows(), p.profileTraces(), p.res.2x()), Christian Keller [ctb] (Functions: histBxp(), p.tachoPlot()), Kjetil Halvorsen [ctb] (Functions: KSd(), ecdf.ksCI()), Alain Hauser [ctb] (Functions: cairoSwd(), is.whole(), toLatex.numeric()*), Christoph Buser [ctb] (to function Duplicated()), Lorenz Gygax [ctb] (to function p.res.2fact()), Bill Venables [ctb] (Functions: empty.dimnames(), primes()), Tony Plate [ctb] (to inv.seq()), Isabelle Fl<fc>ckiger [ctb], Marcel Wolbers [ctb], Markus Keller [ctb], Sandrine Dudoit [ctb], Jane Fridlyand [ctb], Greg Snow [ctb] (to loessDemo()), Henrik Aa. Nielsen [ctb] (to loessDemo()), Vincent Carey [ctb], Ben Bolker [ctb], Philippe Grosjean [ctb], Fr<e9>d<e9>ric Ibanez [ctb], Caterina Savi [ctb], Charles Geyer [ctb], Jens Oehlschl<e4>gel [ctb]

Initial release

2021-04-03