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Create and Set Names for Helmert Contrasts

helm_names.Rd

Create and set column names for Helmert contrasts associated with a factor.

Usage

helm_names(x)

helm_names(x) <- value

Arguments

x

a factor for which the contrast column headings are to be named.

value

a character vector or list of length two (any subsequent elements will be ignored), which are separators used in creating the headings; the first is a "within" separator and the second a "between" separator, see examples.

Details

Helmert contrasts for a factor contrast the second level with the first, the third with the average of the first two, and so on. A contrasts matrix can be set as an attribute of a factor using the function contrasts<-, and using the contrasts function contr.helmert as an argument i.e., contrasts(f)<- contr.helmert, will create and set an appropriate Helmert contrasts matrix attribute. However the columns of the resulting Helmert contrasts matrix are unnamed. helm_names()<- creates these column names based on the names the levels of the factor x.

If factor x does not have an associated Helmert contrast matrix, helm_names()<- will set one, giving a message. The names of the levels of factor x need to be fairly short for function this to be helpful.

The function helm_names() is an alias for contr_colnames and included simply for completeness and to optimise help searches.

See also

contrast, contrasts and contr.helmert.

Other contrast-names: contr_colnames()

Examples

(f <- gl(5, 5, labels = LETTERS[1:5]))
#>  [1] A A A A A B B B B B C C C C C D D D D D E E E E E
#> Levels: A B C D E

contrasts(f)<- contr.helmert
f
#>  [1] A A A A A B B B B B C C C C C D D D D D E E E E E
#> attr(,"contrasts")
#>   [,1] [,2] [,3] [,4]
#> A   -1   -1   -1   -1
#> B    1   -1   -1   -1
#> C    0    2   -1   -1
#> D    0    0    3   -1
#> E    0    0    0    4
#> Levels: A B C D E
helm_names(f)
#> NULL

helm_names(f)<- c(":", "v")
f
#>  [1] A A A A A B B B B B C C C C C D D D D D E E E E E
#> attr(,"contrasts")
#>   A v B A:B v C A:C v D A:D v E
#> A    -1      -1      -1      -1
#> B     1      -1      -1      -1
#> C     0       2      -1      -1
#> D     0       0       3      -1
#> E     0       0       0       4
#> Levels: A B C D E
helm_names(f)
#> [1] "A v B"   "A:B v C" "A:C v D" "A:D v E"

contrasts(f)<- NULL
f
#>  [1] A A A A A B B B B B C C C C C D D D D D E E E E E
#> Levels: A B C D E

helm_names(f)<- c("-", "vs.")
#> Setting Helmert contrasts for factor x with `helm_names()<-`.
f
#>  [1] A A A A A B B B B B C C C C C D D D D D E E E E E
#> attr(,"contrasts")
#>   A vs. B A-B vs. C A-C vs. D A-D vs. E
#> A      -1        -1        -1        -1
#> B       1        -1        -1        -1
#> C       0         2        -1        -1
#> D       0         0         3        -1
#> E       0         0         0         4
#> Levels: A B C D E
helm_names(f)
#> [1] "A vs. B"   "A-B vs. C" "A-C vs. D" "A-D vs. E"

rm(f)