as.fd | R Documentation |
Translate a spline object of another class into the
Functional Data (class fd
) format.
as.fd(x, ...)
## S3 method for class 'fdSmooth'
as.fd(x, ...)
## S3 method for class 'function'
as.fd(x, ...)
## S3 method for class 'smooth.spline'
as.fd(x, ...)
x |
an object to be converted to class |
... |
optional arguments passed to specific methods, currently unused. |
The behavior depends on the class
and nature of x
.
extract the fd
component
Create an fd
object from a function of the form
created by splinefun
. This will translate method
= 'fmn' and 'natural' but not 'periodic': 'fmn' splines
are isomorphic to standard B-splines with coincident
boundary knots, which is the basis produced by
create.bspline.basis
. 'natural' splines occupy
a subspace of this space, with the restriction that the
second derivative at the end points is zero (as noted in
the Wikipedia spline
article). 'periodic' splines
do not use coincident boundary knots and are not
currently supported in fda
; instead, fda
uses finite Fourier bases for periodic phenomena.
Create an fd
object from a smooth.spline
object.
Spencer Graves
Ramsay, James O., Hooker, Giles, and Graves, Spencer (2009), Functional data analysis with R and Matlab, Springer, New York.
Ramsay, James O., and Silverman, Bernard W. (2005), Functional Data Analysis, 2nd ed., Springer, New York.
Ramsay, James O., and Silverman, Bernard W. (2002), Applied Functional Data Analysis, Springer, New York.
spline
entry in Wikipedia
https://en.wikipedia.org/wiki/Spline_(mathematics)
fd
splinefun
##
## as.fd.fdSmooth
##
girlGrowthSm <- with(growth,
smooth.basisPar(argvals=age, y=hgtf, lambda=0.1))
girlGrowth.fd <- as.fd(girlGrowthSm)
##
## as.fd.function(splinefun(...), ...)
##
x2 <- 1:7
y2 <- sin((x2-0.5)*pi)
fd_function <- splinefun(x2, y2)
fd. <- as.fd(fd_function)
x. <- seq(1, 7, .02)
fdx. <- fda::eval.fd(x., fd.)
# range(y2, fx., fdx.) generates an error 2012.04.22
rfdx <- range(fdx.)
oldpar <- par(no.readonly= TRUE)
plot(range(x2), range(y2, fdx., rfdx), type='n')
points(x2, y2)
lines(x., sin((x.-0.5)*pi), lty='dashed')
lines(x., fdx., col='blue')
lines(x., eval.fd(x., fd.), col='red', lwd=3, lty='dashed')
# splinefun and as.fd(splineful(...)) are close
# but quite different from the actual function
# apart from the actual 7 points fitted,
# which are fitted exactly
# ... and there is no information in the data
# to support a better fit!
# Translate also a natural spline
fn <- splinefun(x2, y2, method='natural')
fn. <- as.fd(fn)
lines(x., fn(x.), lty='dotted', col='blue')
lines(x., eval.fd(x., fn.), col='green', lty='dotted', lwd=3)
if(!CRAN()) {
# Will NOT translate a periodic spline
# fp <- splinefun(x, y, method='periodic')
# as.fd(fp)
# Error in as.fd.function(fp) :
# x (fp) uses periodic B-splines, and as.fd is programmed
# to translate only B-splines with coincident boundary knots.
}
##
## as.fd.smooth.spline ... this doesn't work (24 January 2024)
##
#cars.spl <- with(cars, smooth.spline(speed, dist))
#cars.fd <- as.fd(cars.spl)
#plot(dist~speed, cars)
#lines(cars.spl)
#sp. <- with(cars, seq(min(speed), max(speed), len=101))
#d. <- eval.fd(sp., cars.fd)
#lines(sp., d., lty=2, col='red', lwd=3)
par(oldpar)
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