wrapr
introduces an operator called "named map builder" that is written as ":=
". Named map builder is a very simple bit of code that performs a very simple task: it adds names to vectors or lists (making them work more like maps).
Here are some examples:
library("wrapr") 'a' := 5 c('a' := 5, 'b' := 6) c('a', 'b') := c(5, 6)
The left-side argument of the :=
operator is called "the names", and the right-side argument is called "the values". The :=
operators returns the values with the names set to names.
A key use of the named map builder is the following:
key = 'keycode' key := 'value'
Notice the value inside the variable key
was used as the array name, this differs from
what is easily done with R
's native c(key = 'value')
style notation.
A great use of the :=
operator is using it to conveniently build arguments lists for functions such as seplyr::mutate_se()
. This works for simple explicit code such as the following.
library("seplyr") datasets::iris %.>% summarize_se(., "Mean_Sepal_Length" := "mean(Sepal.Length)")
Slightly more complicated code such as:
datasets::iris %.>% group_by_se(., "Species") %.>% summarize_se(., c("Mean_Sepal_Length" := "mean(Sepal.Length)", "Mean_Sepal_Width" := "mean(Sepal.Width)"))
Or even parametric code such as:
resultColumn <- "summary_value" datasets::iris %.>% group_by_se(., "Species") %.>% summarize_se(., resultColumn := "mean(Sepal.Length)")
For more details please see: help(
:=, package = 'wrapr')
and
help("%.>%", package="wrapr")
.
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