jackmds.smacofP function

MDS Jackknife for smacofP objects

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

## 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.

Returns

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

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.

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)