Is there something like a function composition in R?
在R中有像函数合成这样的东西吗?
I think in haskell it's somthing like "(.)" and in agda it's the ring operator.
我认为在haskell中它是“(.)”，在agda中它是环操作符。
Also, I find litte information on high level functional programming in R. I found the Functions "Reduce", "Map", "Filter"..., are there more? Any pointers?
此外，我在r中找到了关于高级函数编程的litte信息，我发现了函数“Reduce”、“Map”、“Filter”……,有更多的吗?指针吗?
2 个解决方案
#1
8
You may make compositing function like this:
你可以把合成函数做成这样:
composite<-function(f,g) function(...) f(g(...))
f<-function(x) x+1;
g<-function(x) x*2;
composite(f,g)(7)
composite(g,f)(7)
or make operator of this.
或者做运算。
About the second point, there are lots of such; I think the most used are the *apply family (sapply, mapply, tapply, lapply, apply...).
关于第二点，有很多这样的;我认为最常用的是*apply family (sapply、mapply、tapply、lapply、apply…)。
#2
16
The functional package has a Compose functional which generalizes to any number of functions:
功能包具有组合功能，可推广到任意数量的功能:
set.seed(123)
x <- matrix(runif(100), 10, 10)
mean(rowSums(scale(x)))
# [1] 5.486063e-18
library(functional)
Compose(scale, rowSums, mean)(x)
# [1] 5.486063e-18
(Note that the functions are applied from left to right.)
(注意，函数是从左到右应用的。)
#1
8
You may make compositing function like this:
你可以把合成函数做成这样:
composite<-function(f,g) function(...) f(g(...))
f<-function(x) x+1;
g<-function(x) x*2;
composite(f,g)(7)
composite(g,f)(7)
or make operator of this.
或者做运算。
About the second point, there are lots of such; I think the most used are the *apply family (sapply, mapply, tapply, lapply, apply...).
关于第二点，有很多这样的;我认为最常用的是*apply family (sapply、mapply、tapply、lapply、apply…)。
#2
16
The functional package has a Compose functional which generalizes to any number of functions:
功能包具有组合功能，可推广到任意数量的功能:
set.seed(123)
x <- matrix(runif(100), 10, 10)
mean(rowSums(scale(x)))
# [1] 5.486063e-18
library(functional)
Compose(scale, rowSums, mean)(x)
# [1] 5.486063e-18
(Note that the functions are applied from left to right.)
(注意，函数是从左到右应用的。)