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Create a skimr function list

Source: R/sfl.R
sfl.Rd

This constructor is used to create a named list of functions. It also you also pass NULL to identify a skimming function that you wish to remove. Only functions that return a single value, working with dplyr::summarize(), can be used within sfl.

Usage

sfl(..., skim_type = "")

Arguments

...

Inherited from dplyr::data_masking() for dplyr version 1 or later or dplyr::funs() for older versions of dplyr. A list of functions specified by:

  • Their name, "mean"

  • The function itself, mean

  • A call to the function with . as a dummy argument, mean(., na.rm = TRUE)

  • An anonymous function in purrr notation, ~mean(., na.rm = TRUE)

skim_type

A character scalar. This is used to match locally-provided skimmers with defaults. See get_skimmers() for more detail.

Value

A skimr_function_list, which contains a list of fun_calls, returned by dplyr::funs() and a list of skimming functions to drop.

Details

sfl() will automatically generate callables and names for a variety of inputs, including functions, formulas and strings. Nonetheless, we recommend providing names when reasonable to get better skim() output.

See also

dplyr::funs(), skim_with() and get_skimmers().

Examples

# sfl's can take a variety of input formats and will generate names
# if not provided.
sfl(mad, "var", ~ length(.)^2)
#> $funs
#> $funs$mad
#> function (x, center = median(x), constant = 1.4826, na.rm = FALSE, 
#>     low = FALSE, high = FALSE) 
#> {
#>     if (na.rm) 
#>         x <- x[!is.na(x)]
#>     n <- length(x)
#>     constant * if ((low || high) && n%%2 == 0) {
#>         if (low && high) 
#>             stop("'low' and 'high' cannot be both TRUE")
#>         n2 <- n%/%2 + as.integer(high)
#>         sort(abs(x - center), partial = n2)[n2]
#>     }
#>     else median(abs(x - center))
#> }
#> <bytecode: 0x55bd1f086768>
#> <environment: namespace:stats>
#> 
#> $funs$`"var"`
#> [1] "var"
#> 
#> $funs$`~length(.)^2`
#> ~length(.)^2
#> <environment: 0x55bd19f42b88>
#> 
#> 
#> $skim_type
#> [1] ""
#> 
#> attr(,"class")
#> [1] "skimr_function_list"

# But these can generate unpredictable names in your output.
# Better to set your own names.
sfl(mad = mad, variance = "var", length_sq = ~ length(.)^2)
#> $funs
#> $funs$mad
#> function (x, center = median(x), constant = 1.4826, na.rm = FALSE, 
#>     low = FALSE, high = FALSE) 
#> {
#>     if (na.rm) 
#>         x <- x[!is.na(x)]
#>     n <- length(x)
#>     constant * if ((low || high) && n%%2 == 0) {
#>         if (low && high) 
#>             stop("'low' and 'high' cannot be both TRUE")
#>         n2 <- n%/%2 + as.integer(high)
#>         sort(abs(x - center), partial = n2)[n2]
#>     }
#>     else median(abs(x - center))
#> }
#> <bytecode: 0x55bd1f086768>
#> <environment: namespace:stats>
#> 
#> $funs$variance
#> [1] "var"
#> 
#> $funs$length_sq
#> ~length(.)^2
#> <environment: 0x55bd19f42b88>
#> 
#> 
#> $skim_type
#> [1] ""
#> 
#> attr(,"class")
#> [1] "skimr_function_list"

# sfl's can remove individual skimmers from defaults by passing NULL.
sfl(hist = NULL)
#> $funs
#> $funs$hist
#> NULL
#> 
#> 
#> $skim_type
#> [1] ""
#> 
#> attr(,"class")
#> [1] "skimr_function_list"

# When working interactively, you don't need to set a type.
# But you should when defining new defaults with `get_skimmers()`.
get_skimmers.my_new_class <- function(column) {
  sfl(n_missing, skim_type = "my_new_class")
}