R: Standard Deviation of Functional Data

sd.fd {fda} | R Documentation

## Standard Deviation of Functional Data

### 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))

[Package fda version 2.4.8 Index]