expss (version 0.11.4)

keep: Keep or drop elements by name/criteria in data.frame/matrix

Description

keep selects variables/elements from data.frame by their names or by criteria (see criteria). except drops variables/elements from data.frame by their names or by criteria. Names at the top-level can be unquoted (non-standard evaluation). For standard evaluation of parameters you can surround them by round brackets. See examples. Methods for list will apply keep/except to each element of the list separately.

Usage

keep(data, ...)
except(data, ...)

Value

object of the same type as data

Arguments

data

data.frame/matrix/list

...

column names of type character/numeric or criteria/logical functions

Examples

data(iris)
columns(iris, Sepal.Length, Sepal.Width)  
columns(iris, -Species)

columns(iris, Species, "^.") # move 'Species' to the first position

columns(iris, -"^Petal") # remove columns which names start with 'Petal'

columns(iris, -5) # remove fifth column

data(mtcars)
columns(mtcars, mpg:qsec) # keep columns from 'mpg' to 'qsec'
columns(mtcars, mpg %to% qsec) # the same result

 # standard and non-standard evaluation
 many_vars = c("am", "vs", "cyl")
 columns(mtcars, many_vars)
 
# character expansion
dfs = data.frame(
     a =   rep(10, 5),
     b_1 = rep(11, 5),
     b_2 = rep(12, 5),
     b_3 = rep(12, 5),
     b_4 = rep(14, 5),
     b_5 = rep(15, 5) 
 )
 i = 1:5
 columns(dfs, b_1 %to% b_5) 
 columns(dfs, "b_{i}") # the same result