sd: Standard Deviation of Functional Data

In fda: Functional Data Analysis

Description

Evaluate the standard deviation of a set of functions in a functional data object.

Usage

sd.fd(fdobj)
std.fd(fdobj)
stdev.fd(fdobj)
stddev.fd(fdobj)

Arguments

fdobj

a functional data object.

Details

The multiple aliases are provided for compatibility with previous versions and with other languages. The name for the standard deviation function in R is 'sd'. Matlab uses 'std'. S-Plus and Microsoft Excal use 'stdev'. 'stddev' was used in a previous version of the 'fda' package and is retained for compatibility.

Value

a functional data object with a single replication that contains the standard deviation of the one or several functions in the object fdobj.

See Also

mean.fd, sum.fd, center.fd

Examples

liptime  <- seq(0,1,.02)
liprange <- c(0,1)

#  -------------  create the fd object -----------------
#       use 31 order 6 splines so we can look at acceleration

nbasis <- 51
norder <- 6
lipbasis <- create.bspline.basis(liprange, nbasis, norder)
lipbasis <- create.bspline.basis(liprange, nbasis, norder)

#  ------------  apply some light smoothing to this object  -------

Lfdobj   <- int2Lfd(4)
lambda   <- 1e-12
lipfdPar <- fdPar(lipbasis, Lfdobj, lambda)

lipfd <- smooth.basis(liptime, lip, lipfdPar)$fd
names(lipfd$fdnames) = c("Normalized time", "Replications", "mm")

lipstdfd <- sd.fd(lipfd)
plot(lipstdfd)

all.equal(lipstdfd, std.fd(lipfd))
all.equal(lipstdfd, stdev.fd(lipfd))
all.equal(lipstdfd, stddev.fd(lipfd))

fda documentation built on May 2, 2019, 5:12 p.m.