OpenRepGrid (version 0.1.9)

ssq: Calculate SSQ (accuracy) of biplot representation for elements and constructs.

Description

Each construct and element are vectors in a multidimensional space. When reducing the representation to a lower dimensional space, a loss of information (sum-of-squares) will usually occur. The output of the function shows the proportion of sum-of-squares (SSQ) explained for the elements (constructs) and the amount explained by each principal component. This allows to assess which elements (construct) are represented how well in the current representation. Also it shows how much of the total variation is explained.

Usage

ssq(x, along = 2, center = 1, normalize = 0, g = 0, h = 1 - g,
  col.active = NA, col.passive = NA, ...)

Arguments

x

repgrid object.

along

Numeric. Table of sum-of-squares (SSQ) for 1=constructs, 2=elements (default). Note that currently these calculations only make sense for biplot reperesentations with g=1 and h=1 respectively.

center

Numeric. The type of centering to be performed. 0= no centering, 1= row mean centering (construct), 2= column mean centering (elements), 3= double-centering (construct and element means), 4= midpoint centering of rows (constructs). The default is 1<

normalize

A numeric value indicating along what direction (rows, columns) to normalize by standard deviations. 0 = none, 1= rows, 2 = columns (default is 0).

g

Power of the singular value matrix assigned to the left singular vectors, i.e. the constructs.

h

Power of the singular value matrix assigned to the right singular vectors, i.e. the elements.

col.active

Columns (elements) that are no supplementary points, i.e. they are used in the SVD to find principal components. default is to use all elements.

col.passive

Columns (elements) that are supplementary points, i.e. they are NOT used in the SVD but projecte into the component space afterwards. They do not determine the solution. Default is NA, i.e. no elements are set supplementary.

Value

• A list containing three wo elements
• ssq.table
  dataframe with sum-of-squares explained for element/construct by each dimension
• ssq.table.cumsum
  dataframe with cumulated sum-of-squares explained for element/construct number of dimensions
• ssq.total
  total sum-of-squares after pre-transforming grid matrix

Examples

# explained sum-of-squares for elements
 ssq(bell2010)

 # explained sum-of-squares for constructs
 ssq(bell2010, along=1)

 # save results
 s <- ssq(bell2010)

 # printing options
 print(s)
 print(s, digits=4)
 print(s, dim=3)
 print(s, cumulated=FALSE)

 # access results
 names(s)
 s$ssq.table
 s$ssq.table.cumsum
 s$ssq.total