Separate a character column into multiple columns with a regular expression or numeric locations
Source:R/step-subset-separate.R
separate.dtplyr_step.Rd
This is a method for the tidyr::separate()
generic. It is translated to
data.table::tstrsplit()
in the j
argument of [.data.table
.
Usage
# S3 method for class 'dtplyr_step'
separate(
data,
col,
into,
sep = "[^[:alnum:]]+",
remove = TRUE,
convert = FALSE,
...
)
Arguments
- data
A
lazy_dt()
.- col
Column name or position.
This argument is passed by expression and supports quasiquotation (you can unquote column names or column positions).
- into
Names of new variables to create as character vector. Use
NA
to omit the variable in the output.- sep
Separator between columns. The default value is a regular expression that matches any sequence of non-alphanumeric values.
- remove
If TRUE, remove the input column from the output data frame.
- convert
If TRUE, will run type.convert() with as.is = TRUE on new columns. This is useful if the component columns are integer, numeric or logical.
NB: this will cause string "NA"s to be converted to NAs.
- ...
Arguments passed on to methods
Examples
library(tidyr)
# If you want to split by any non-alphanumeric value (the default):
df <- lazy_dt(data.frame(x = c(NA, "x.y", "x.z", "y.z")), "DT")
df %>% separate(x, c("A", "B"))
#> Source: local data table [4 x 2]
#> Call: copy(DT)[, `:=`(c("A", "B"), tstrsplit(x, split = "[^[:alnum:]]+"))][,
#> `:=`("x", NULL)]
#>
#> A B
#> <chr> <chr>
#> 1 NA NA
#> 2 x y
#> 3 x z
#> 4 y z
#>
#> # Use as.data.table()/as.data.frame()/as_tibble() to access results
# If you just want the second variable:
df %>% separate(x, c(NA, "B"))
#> Source: local data table [4 x 1]
#> Call: copy(DT)[, `:=`("B", tstrsplit(x, split = "[^[:alnum:]]+", keep = 2L))][,
#> `:=`("x", NULL)]
#>
#> B
#> <chr>
#> 1 NA
#> 2 y
#> 3 z
#> 4 z
#>
#> # Use as.data.table()/as.data.frame()/as_tibble() to access results
# Use regular expressions to separate on multiple characters:
df <- lazy_dt(data.frame(x = c(NA, "x?y", "x.z", "y:z")), "DT")
df %>% separate(x, c("A","B"), sep = "([.?:])")
#> Source: local data table [4 x 2]
#> Call: copy(DT)[, `:=`(c("A", "B"), tstrsplit(x, split = "([.?:])"))][,
#> `:=`("x", NULL)]
#>
#> A B
#> <chr> <chr>
#> 1 NA NA
#> 2 x y
#> 3 x z
#> 4 y z
#>
#> # Use as.data.table()/as.data.frame()/as_tibble() to access results
# convert = TRUE detects column classes:
df <- lazy_dt(data.frame(x = c("x:1", "x:2", "y:4", "z", NA)), "DT")
df %>% separate(x, c("key","value"), ":") %>% str
#> List of 12
#> $ parent :List of 12
#> ..$ parent :List of 8
#> .. ..$ parent :Classes ‘data.table’ and 'data.frame': 5 obs. of 1 variable:
#> .. .. ..$ x: chr [1:5] "x:1" "x:2" "y:4" "z" ...
#> .. .. ..- attr(*, ".internal.selfref")=<externalptr>
#> .. ..$ vars : chr "x"
#> .. ..$ groups : chr(0)
#> .. ..$ locals : list()
#> .. ..$ implicit_copy: logi FALSE
#> .. ..$ needs_copy : logi FALSE
#> .. ..$ env :<environment: 0x55b20715cda0>
#> .. ..$ name : symbol DT
#> .. ..- attr(*, "class")= chr [1:2] "dtplyr_step_first" "dtplyr_step"
#> ..$ vars : chr [1:3] "x" "key" "value"
#> ..$ groups : chr(0)
#> ..$ locals : list()
#> ..$ implicit_copy : logi TRUE
#> ..$ needs_copy : logi TRUE
#> ..$ env :<environment: 0x55b20715cda0>
#> ..$ arrange : NULL
#> ..$ i : NULL
#> ..$ j : language `:=`(c("key", "value"), tstrsplit(x, split = ":"))
#> ..$ on : chr(0)
#> ..$ allow_cartesian: NULL
#> ..- attr(*, "class")= chr [1:2] "dtplyr_step_subset" "dtplyr_step"
#> $ vars : chr [1:2] "key" "value"
#> $ groups : chr(0)
#> $ locals : list()
#> $ implicit_copy : logi TRUE
#> $ needs_copy : logi TRUE
#> $ env :<environment: 0x55b20715cda0>
#> $ arrange : NULL
#> $ i : NULL
#> $ j : language `:=`("x", NULL)
#> $ on : chr(0)
#> $ allow_cartesian: NULL
#> - attr(*, "class")= chr [1:2] "dtplyr_step_subset" "dtplyr_step"
df %>% separate(x, c("key","value"), ":", convert = TRUE) %>% str
#> List of 12
#> $ parent :List of 12
#> ..$ parent :List of 8
#> .. ..$ parent :Classes ‘data.table’ and 'data.frame': 5 obs. of 1 variable:
#> .. .. ..$ x: chr [1:5] "x:1" "x:2" "y:4" "z" ...
#> .. .. ..- attr(*, ".internal.selfref")=<externalptr>
#> .. ..$ vars : chr "x"
#> .. ..$ groups : chr(0)
#> .. ..$ locals : list()
#> .. ..$ implicit_copy: logi FALSE
#> .. ..$ needs_copy : logi FALSE
#> .. ..$ env :<environment: 0x55b20715cda0>
#> .. ..$ name : symbol DT
#> .. ..- attr(*, "class")= chr [1:2] "dtplyr_step_first" "dtplyr_step"
#> ..$ vars : chr [1:3] "x" "key" "value"
#> ..$ groups : chr(0)
#> ..$ locals : list()
#> ..$ implicit_copy : logi TRUE
#> ..$ needs_copy : logi TRUE
#> ..$ env :<environment: 0x55b20715cda0>
#> ..$ arrange : NULL
#> ..$ i : NULL
#> ..$ j : language `:=`(c("key", "value"), tstrsplit(x, split = ":", type.convert = TRUE))
#> ..$ on : chr(0)
#> ..$ allow_cartesian: NULL
#> ..- attr(*, "class")= chr [1:2] "dtplyr_step_subset" "dtplyr_step"
#> $ vars : chr [1:2] "key" "value"
#> $ groups : chr(0)
#> $ locals : list()
#> $ implicit_copy : logi TRUE
#> $ needs_copy : logi TRUE
#> $ env :<environment: 0x55b20715cda0>
#> $ arrange : NULL
#> $ i : NULL
#> $ j : language `:=`("x", NULL)
#> $ on : chr(0)
#> $ allow_cartesian: NULL
#> - attr(*, "class")= chr [1:2] "dtplyr_step_subset" "dtplyr_step"