powerStressFast: Power stress minimization by NEWUOA

In cops: Cluster Optimized Proximity Scaling

Power stress minimization by NEWUOA

Description

An implementation to minimize power stress by a derivative-free trust region optimization algorithm (NEWUOA). Much faster than majorizing as used in powerStressMin but perhaps less accurate.

Usage

powerStressFast(
  delta,
  kappa = 1,
  lambda = 1,
  nu = 1,
  weightmat = 1 - diag(nrow(delta)),
  init = NULL,
  ndim = 2,
  acc = 1e-12,
  itmax = 50000,
  verbose = FALSE
)

Arguments

delta	dist object or a symmetric, numeric data.frame or matrix of distances
kappa	power of the transformation of the fitted distances; defaults to 1
lambda	the power of the transformation of the proximities; defaults to 1
nu	the power of the transformation for weightmat; defaults to 1
weightmat	a matrix of finite weights
init	starting configuration
ndim	dimension of the configuration; defaults to 2
acc	The smallest value of the trust region radius that is allowed. If not defined, then 1e-10 will be used.
itmax	maximum number of iterations. Default is 50000.
verbose	should iteration output be printed; if > 1 then yes

Value

a smacofP object (inheriting form smacofB, see smacofSym). It is a list with the components

• delta: Observed dissimilarities, not normalized

• obsdiss: Observed dissimilarities, normalized

• confdist: Configuration dissimilarities, NOT normalized

• conf: Matrix of fitted configuration, NOT normalized

• stress: Default stress (stress 1, square root of the explicitly normalized stress on the normalized, transformed dissimilarities)

• spp: Stress per point (based on stress.en)

• ndim: Number of dimensions

• model: Name of smacof model

• niter: Number of iterations

• nobj: Number of objects

• type: Type of MDS model

and some additional components

• gamma: Empty

• stress.m: default stress for the COPS and STOP. Defaults to the explicitly normalized stress on the normalized, transformed dissimilarities

• stress.en: explicitly stress on the normalized, transformed dissimilarities and normalized transformed distances

• deltaorig: observed, untransformed dissimilarities

• weightmat: weighting matrix

See Also

smacofSym

Examples

dis<-smacof::kinshipdelta
res<-powerStressFast(as.matrix(dis),kappa=2,lambda=1.5)
res
summary(res)
plot(res)

cops documentation built on Jan. 22, 2023, 1:47 a.m.