to.map {rmr2} | R Documentation |
These utility functions are meant to avoid the little boilerplate code necessary to convert ordinary functions into map and reduce functions.
to.map(fun1, fun2 = identity) to.reduce(fun1, fun2 = identity)
fun1 |
A function to apply to the key, or to the key-value pair if the second argument is missing |
fun2 |
A function to apply to the value |
Sometimes there are functions that we could use almost directly as map or reduce functions but for a bit of boilerplate code, and
we hate boilerplate code. That's where the functions documented herein can help. They take one or two functions of a single argument and
return a valid map or reduce function. In the case of to.map
when two functions are specified they are applied independently to the
key and the value and the return values are returned as a key-value pair; when only one is, it is applied to the key-value pair. For
to.reduce
the behavior is the same.
##The identity map: to.map(identity) ## equivalent to function(k, v) keyval(k, v) ##Replace key with mod 10 of the key and pass the value along: to.map(function(x) x %% 10, identity ) ##Sum up all the values for the same key: to.reduce(identity, function(vv) sum(vv))