curve_srvf_align {fdasrvf}

Align Curves

Description

Aligns a collection of curves using the elastic square-root velocity (srvf) framework. If the curves are describing multidimensional functional data, then rotated == FALSE and mode == 'O'

Usage

curve_srvf_align(
  beta,
  mode = "O",
  rotated = TRUE,
  scale = FALSE,
  lambda = 0,
  maxit = 20,
  ms = "mean"
)

Arguments

beta

Array of sizes n \times T \times N for N curves of dimension n evaluated on a grid of T points

mode

Open ("O") or Closed ("C") curves

rotated

Optimize over rotation (default = TRUE)

scale

Include scale (default = FALSE)

lambda

A numeric value specifying the elasticity. Defaults to 0.0.

maxit

maximum number of iterations

ms

string defining whether the Karcher mean ("mean") or Karcher median ("median") is returned (default = "mean")

Value

Returns a list containing

betan

aligned curves

qn

aligned srvfs

betamean

mean curve

q_mu

mean SRVFs

References

Srivastava, A., Klassen, E., Joshi, S., Jermyn, I., (2011). Shape analysis of elastic curves in euclidean spaces. Pattern Analysis and Machine Intelligence, IEEE Transactions on 33 (7), 1415-1428.

Examples

data("mpeg7")
# note: use more shapes and iterations, small for speed
out = curve_srvf_align(beta[,,1,1:2],maxit=2)