register.fd {fda} | R Documentation |
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.
register.fd(y0fd, yfd, WfdParobj, conv=1e-04, iterlim=20, dbglev=1, periodic=FALSE, crit=2)
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 $h(t)$. |
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 TRUE , 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. |
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.
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. |
#See the analyses of the growth data for examples.