如何在R中提取1x1数组切片作为矩阵？ [英] how to extract 1x1 array slice as matrix in R?

问题描述

我正在使用3D数组。函数从用户获取2D数组切片（矩阵），并使用行和列名称（数组的相应dimnames）将其可视化。如果数组维度> 1，它可以正常工作。

I am working with 3D arrays. A function takes a 2D array slice (matrix) from the user and visualizes it, using row and column names (the corresponding dimnames of the array). It works fine if the array dimensions are > 1.

但是，如果我有1x1x1数组，我无法将切片提取为矩阵：

However, if I have 1x1x1 array, I cannot extract the slice as a matrix:

a <- array(1, c(1,1,1), list(A="a", B="b", C="c"))

a[1,,]
[1] 1

这是一个没有dimnames的标量，因此缺少部分必要信息。如果我添加 drop = FALSE ，我没有得到矩阵但保留原始数组：

It is a scalar with no dimnames, hence part of the necessary information is missing. If I add drop=FALSE, I don't get a matrix but retain the original array:

a[1,,,drop=FALSE]
, , C = c

   B
A   b
  a 1

这些dimnames在这里，但它仍然是3维的。有没有一种简单的方法可以从1x1x1数组获得一个如上所示的矩阵切片，只是没有第三维：

The dimnames are here but it is still 3-dimensional. Is there an easy way to get a matrix slice from 1x1x1 array that would look like the above, just without the third dimension:

   B
A   b
  a 1

我怀疑问题在于索引数组，我们无法区分'take 1 value'和'take all values'以防'all'只是一个单独的...

I suspect the issue is that when indexing an array, we cannot distinguish between 'take 1 value' and 'take all values' in case where 'all' is just a singleton...

推荐答案

的 drop 参数是全有或全无，但 abind 包中有一个 adrop 函数，可让您选择要删除的维度：

The drop parameter of [ is all-or-nothing, but the abind package has an adrop function which will let you choose which dimension you want to drop:

abind::adrop(a, drop = 3)
##    B
## A   b
##   a 1

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