如何将数据帧转换为R中一个三维阵列 [英] How to convert a data frame to a 3d array in R

问题描述

我有，我想转换为三维数组的数据帧。一个在数据帧中的列应作为分裂帧成可组合成阵列二维矩阵分组变量。在下面的最小工作实施例中，数据帧应当被分成由变量i，再组合成4x4x2阵列矩阵。该解决方案应该是大型数据集实用和理想可以推广到数据帧转换为A N维数组。

I have a data frame that I want to convert to a three-dimensional array. One of the columns in the data frame should serve as the grouping variable for splitting the frame into 2d matrices that can be combined into the array. In the following minimal working example, the data frame should be split into matrices by the variable "i", then combined into a 4x4x2 array. The solution should be practical for large data sets and ideally could be generalized to convert a data frame into a n dimensional array.

# Make reproducible 
set.seed(123)

df <- {
  data.frame(i=rep(1:2, each=4),
             x=rep(rep(0:1, each=2), 2),
             y=rep(rep(0:1, 2), 2),
             l=rnorm(8))
}

df
#   i x y           l
# 1 1 0 0 -0.56047565
# 2 1 0 1 -0.23017749
# 3 1 1 0  1.55870831
# 4 1 1 1  0.07050839
# 5 2 0 0  0.12928774
# 6 2 0 1  1.71506499
# 7 2 1 0  0.46091621
# 8 2 1 1 -1.26506123

请注意：我怀疑哈德利韦翰的plyr可以提供所需的工具，也许daply

Note: I suspect that Hadley Wickham's plyr may provide the needed tool, perhaps daply?

推荐答案

下面是我可能会做的：

library(abind)
abind(split(df, df$i), along=3)
# , , 1
# 
#   i x y           l
# 5 1 0 0 -0.56047565
# 6 1 0 1 -0.23017749
# 7 1 1 0  1.55870831
# 8 1 1 1  0.07050839
# 
# , , 2
# 
#   i x y          l
# 5 2 0 0  0.1292877
# 6 2 0 1  1.7150650
# 7 2 1 0  0.4609162
# 8 2 1 1 -1.2650612

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