Center variable

Center a variable by subtracting the mean from each element. Centering can be performed by the grand mean when by = NULL (the default), or by group means when by is a factor variable.

center_variable(variable, scale = FALSE, by = NULL)

Arguments

variable	A numeric vector.
scale	A logical vector. If scale = TRUE, the centered values of variable are divided by their standard deviation.
by	A vector with the factor class.

Value

A numeric vector.

Examples

df <- data.frame(
  id = 1:20,
  group = as.factor(sample(c("A", "B"), 20, replace = TRUE)),
  body_mass = rnorm(20, mean = 65, sd = 12)
)

df$body_mass_centered <- center_variable(df$body_mass, by = df$group)
df
#>    id group body_mass body_mass_centered
#> 1   1     B  73.58482          7.9011490
#> 2   2     B  51.93189        -13.7517821
#> 3   3     B  69.81828          4.1346143
#> 4   4     A  69.85134          4.4779158
#> 5   5     B  89.51611         23.8324393
#> 6   6     B  78.66696         12.9832899
#> 7   7     A  55.67533         -9.6980863
#> 8   8     A  61.63453         -3.7388853
#> 9   9     A  68.56865          3.1952274
#> 10 10     A  62.17225         -3.2011733
#> 11 11     A  65.53202          0.1585967
#> 12 12     B  39.56360        -26.1200650
#> 13 13     B  61.05810         -4.6255702
#> 14 14     B  70.54463          4.8609601
#> 15 15     B  73.32349          7.6398246
#> 16 16     A  56.49687         -8.8765528
#> 17 17     A  62.49324         -2.8801821
#> 18 18     B  69.22735          3.5436825
#> 19 19     A  85.93656         20.5631399
#> 20 20     B  45.28513        -20.3985425