Register Functional Data Objects Using a Continuous Criterion
register.fd |
Language Reference for FDA Library
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Register Functional Data Objects Using a Continuous Criterion
DESCRIPTION:
Curves are aligned with a target or template curve using a continuous
criterion. By aligned is meant that the shape of each curve is matched
as closely as possible to that of the target by means of a smooth
increasing transformation of the argument, or a warping function.
USAGE:
register.fd(y0fd, yfd, WfdParobj, conv=0.01,
iterlim=10, dbglev=1, periodic=F, crit=2)
REQUIRED ARGUMENTS:
- y0fd
-
a functional data object defining the target for registration.
It must be univariate and it must define a single functional
observation.
- yfd
-
a functional data object defining the functions to be registered to
target yfd0.
- WfdParobj
-
a functional parameter object for a single function. This function
is used as the initial value in the estimation of a function
W(t) that defines the warping function h(t) that
registers a particular curve. The object also contains information
on a roughness penalty and smoothing parameter to control the
roughness of h(t).
OPTIONAL ARGUMENTS:
- conv
-
a criterion for convergence of the iterations.
- iterlim
-
a limit on the number of iterations.
- dbglev
-
either 0, 1, or 2. This controls the amount information printed out on
each iteration, with 0 implying no output, 1 intermediate output level,
and 2 full output. If output is desired, it is helpful to turn off
the output buffering option of S-PLUS.
- periodic
-
a logical variable:
if
T
, the functions are considered to be
periodic, in which case a constant can be added to all argument
values after they are warped.
- crit
-
an integer that is either 1 or 2 that indicates the nature of the
continuous registration criterion that is used. If 1, the criterion is
least squares, and if 2, the criterion is the minimum eigenvalue of a
cross-product matrix. In general, criterion 2 is to be preferred.
VALUE:
a named list of length 3 containing the following components:
- regfd
-
A functional data object containing the registered functions.
- Wfd
-
A functional data object containing the functions h
W(t) that define the warping functions h(t).
- shift
-
If the functions are periodic, this is a vector of time shifts.
DETAILS:
The warping function that smoothly and monotonely transforms the
argument is defined by Wfd is the same as that
defines the monotone
smoothing function in for function smooth.monotone. See the
help file for that function for further details.
SEE ALSO:
registerC.fd, smooth.monotone, smooth.morph
EXAMPLES:
See the analyses of the growth data for examples.