Estimates a Smooth Warping Function
smooth.morph
Language Reference for FDA Library

Estimates a Smooth Warping Function

DESCRIPTION:

This function is nearly identical to smooth.monotone but is intended to compute a smooth monotone transformation h(t) of argument t such that h(0) = 0 and h(T) = T, where t is the upper limit of t. This function is used primarily to register curves.

USAGE:

smooth.morph(x, y, WfdParobj, wt=rep(1,nobs),
             conv=.0001, iterlim=20,
             active=c(F,rep(T,ncvec-1)),
             dbglev=1)

REQUIRED ARGUMENTS:

x
a vector of argument values.
y
a vector of data values. This function can only smooth one set of data at a time.
WfdParobj
a functional parameter object that provides an initial value for the coefficients defining function W(t), and a roughness penalty on this function.

OPTIONAL ARGUMENTS:

wt
a vector of weights to be used in the smoothing.
conv
a convergence criterion.
iterlim
the maximum number of iterations allowed in the minimization of error sum of squares.
active
a logical vector specifying which coefficients defining W(t) are estimated. Normally, the first coefficient is fixed.
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 either level 1 or 2 is specified, it can be helpful to turn off the output buffering feature of S-PLUS.

VALUE:

A named list of length 4 containing:
Wfdobj
a functional data object defining function W(x) that that optimizes the fit to the data of the monotone function that it defines.
Flist
a named list containing three results for the final converged solution: (1) f: the optimal function value being minimized, (2) grad: the gradient vector at the optimal solution, and (3) norm: the norm of the gradient vector at the optimal solution.
iternum
the number of iterations.
iternum
the number of iterations.
iterhist
a >iternum+1> by 5 matrix containing the iteration history.

SEE ALSO:

smooth.monotone, landmarkreg, register.fd