列表列表中向量的均值 [英] Mean of vector inside of list of lists

问题描述

我有一个具有以下结构的列表列表:

I have a list of lists with the following structure:

> mylist <- list(list(a=as.numeric(1:3), b=as.numeric(4:6)), 
                 list(a=as.numeric(6:8), b=as.numeric(7:9)))
> str(mylist)
List of 2
 $ :List of 2
  ..$ a: num [1:3] 1 2 3
  ..$ b: num [1:3] 4 5 6
 $ :List of 2
  ..$ a: num [1:3] 6 7 8
  ..$ b: num [1:3] 7 8 9

我想获得mylist的向量a和b之间的逐元素均值.对于向量a，结果将是这样:

I would like to get the element-wise mean between the vectors a and b of mylist. For the vector a, the result would be this:

> a
[1] 3.5 4.5 5.5

我知道函数lapply，rbind和colMeans，但是我无法解决它们的问题.我该如何实现自己的需求?

I know the functions lapply, rbind and colMeans but I can't solve the problem with them. How can I achieve what I need?

推荐答案

另一个想法:

tmp = unlist(mylist, F)
sapply(unique(names(tmp)), 
       function(x) colMeans(do.call(rbind, tmp[grep(x, names(tmp))])))
#       a   b
#[1,] 3.5 5.5
#[2,] 4.5 6.5
#[3,] 5.5 7.5

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