Compute grand-mean centered variables. Usually used for GLM interaction-term predictors and HLM level-2 predictors.
Usage
grand_mean_center(data, vars = names(data), std = FALSE, add.suffix = "")Arguments
- data
Data object.
- vars
Variable(s) to be centered.
- std
Standardized or not. Defaults to
FALSE.- add.suffix
The suffix of the centered variable(s). Defaults to
"". You may set it to"_c","_center", etc.
Examples
d = data.table(a=1:5, b=6:10)
d.c = grand_mean_center(d, "a")
d.c
#> a b
#> 1: -2 6
#> 2: -1 7
#> 3: 0 8
#> 4: 1 9
#> 5: 2 10
d.c = grand_mean_center(d, c("a", "b"), add.suffix="_center")
d.c
#> a b a_center b_center
#> 1: 1 6 -2 -2
#> 2: 2 7 -1 -1
#> 3: 3 8 0 0
#> 4: 4 9 1 1
#> 5: 5 10 2 2