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
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)")
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