jackmds.smacofP {smacofx}

MDS Jackknife for smacofP objects

Description

These functions perform an MDS Jackknife and plot the corresponding solution.

Usage

## S3 method for class 'smacofP'
jackmds(object, eps = 1e-06, itmax = 100, verbose = FALSE)

Arguments

object

Object of class smacofP if used as method or another object inheriting from smacofB (needs to be called directly as jackmds.smacofP then).

eps

Convergence criterion

itmax

Maximum number of iterations

verbose

If 'TRUE', intermediate stress is printed out.

Details

In order to examine the stability solution of an MDS, a Jackknife on the configurations can be performed (see de Leeuw & Meulman, 1986) and plotted. The plot shows the jackknife configurations which are connected to their centroid. In addition, the original configuration (transformed through Procrustes) is plotted. The Jackknife function itself returns also a stability measure (as ratio of between and total variance), a measure for cross validity, and the dispersion around the original smacof solution.

Value

An object of class 'smacofJK', see jackmds. With values

• smacof.conf: Original configuration

• jackknife.confboot: An array of n-1 configuration matrices for each Jackknife MDS solution

• comparison.conf: Centroid Jackknife configurations (comparison matrix)

• cross: Cross validity

• stab: Stability coefficient

• disp: Dispersion

• loss: Value of the loss function (just used internally)

• ndim: Number of dimensions

• call: Model call

• niter: Number of iterations

• nobj: Number of objects

Examples

dats <- na.omit(smacof::PVQ40[,1:5])
diss <- dist(t(dats))   ## Euclidean distances
fit <- rStressMin(diss,type="ordinal",r=0.4,itmax=1000) ## 2D ordinal MDS

res.jk <- jackmds(fit)
plot(res.jk, col.p = "black", col.l = "gray")
plot(res.jk, hclpar = list(c = 80, l = 40))
plot(res.jk, hclpar = list(c = 80, l = 40), plot.lines = FALSE)