Contrast Matrices

Returns a matrix of contrasts.

contr.dummy(n, contrasts = TRUE)
contr.ordinal(n, contrasts = TRUE)
contr.metric(n, contrasts = TRUE)

Arguments

n	A vector containing levels of a factor, or the number of levels.
contrasts	A logical value indicating whether contrasts should be computed.

Details

contr.dummy is standard dummy-coding, contr.metric has the same effect like as.numeric (makes sense of course only for ordered variables). contr.ordinal computes contrasts for ordinal variables.

Value

A matrix with n rows and n-1 columns for contr.ordinal, a matrix with n rows and n columns for contr.dummy and a vector of length n for contr.metric.

References

Hechenbichler K. and Schliep K.P. (2004) Weighted k-Nearest-Neighbor Techniques and Ordinal Classification, Discussion Paper 399, SFB 386, Ludwig-Maximilians University Munich (https://doi.org/10.5282/ubm/epub.1769)

See also

contrasts, contr.poly and contr.sdif

Examples

contr.metric(5)
#>   [,1]
#> 1   -2
#> 2   -1
#> 3    0
#> 4    1
#> 5    2
contr.ordinal(5)
#>   [,1] [,2] [,3] [,4]
#> 1  0.5  0.5  0.5  0.5
#> 2 -0.5  0.5  0.5  0.5
#> 3 -0.5 -0.5  0.5  0.5
#> 4 -0.5 -0.5 -0.5  0.5
#> 5 -0.5 -0.5 -0.5 -0.5
contr.dummy(5)
#>   1 2 3 4 5
#> 1 1 0 0 0 0
#> 2 0 1 0 0 0
#> 3 0 0 1 0 0
#> 4 0 0 0 1 0
#> 5 0 0 0 0 1