r - 如何对 data.frames 列表进行子集化？

Question

我有一个 data.frames 列表，想对一部分数据帧进行子集化。在这种情况下，我想将 mainlist 的 sublist1 和 sublist2 中的 rainfall 和 yield 子集并创建一个新的名为 mainlist_new 的列表。

但是我遇到了这个错误Error in mainlist[[1]][[, 2:3]] : incorrect number of subscripts。

有什么想法和想法吗？

这里是代码和创建的数据

> df1 <- data.frame(station = c("MADA1", "MADA2", "MADA3", "MADA4", "MADA5"),
+                  rainfall = c(0, 5, 10, 15, 20),
+                  yield = c(2000, 3000, 4000, 5000, 6000))
> df2 <- df1
> df3 <- df1
> 
> list_1 <- list(df1, df2, df3)
> 
> list_2 <- list(df1, df2, df3)
> 
> mainlist <- list(list_1, list_2)
> names(mainlist) <- c("sublist1", 'sublist2')
> names(mainlist[[1]]) <- c("station", "rainfall", "yield")
> names(mainlist[[2]]) <-  c("station", "rainfall", "yield")
> 
> names(mainlist)
[1] "sublist1" "sublist2"
> names(mainlist[[1]])
[1] "station"  "rainfall" "yield"   
> 
> # subset `rainfall` and `yield` is sublist1 and sublist2 and create a a new list
> mainlist_new <- list()
> mainlist_new[[1]] <- mainlist[[1]][[,2:3]] 
Error in mainlist[[1]][[, 2:3]] : incorrect number of subscripts
> mainlist_new[[2]] <- mainlist[[2]][[,2:3]] 
Error in mainlist[[2]][[, 2:3]] : incorrect number of subscripts
>

Answer 1

如果我们想根据名称对 list 元素进行子集化

mainlist_new <- lapply(mainlist, `[`, c("rainfall", "yield"))

-输出

> str(mainlist_new)
List of 2
 $ :List of 2
  ..$ rainfall:'data.frame':    5 obs. of  3 variables:
  .. ..$ station : chr [1:5] "MADA1" "MADA2" "MADA3" "MADA4" ...
  .. ..$ rainfall: num [1:5] 0 5 10 15 20
  .. ..$ yield   : num [1:5] 2000 3000 4000 5000 6000
  ..$ yield   :'data.frame':    5 obs. of  3 variables:
  .. ..$ station : chr [1:5] "MADA1" "MADA2" "MADA3" "MADA4" ...
  .. ..$ rainfall: num [1:5] 0 5 10 15 20
  .. ..$ yield   : num [1:5] 2000 3000 4000 5000 6000
 $ :List of 2
  ..$ rainfall:'data.frame':    5 obs. of  3 variables:
  .. ..$ station : chr [1:5] "MADA1" "MADA2" "MADA3" "MADA4" ...
  .. ..$ rainfall: num [1:5] 0 5 10 15 20
  .. ..$ yield   : num [1:5] 2000 3000 4000 5000 6000
  ..$ yield   :'data.frame':    5 obs. of  3 variables:
  .. ..$ station : chr [1:5] "MADA1" "MADA2" "MADA3" "MADA4" ...
  .. ..$ rainfall: num [1:5] 0 5 10 15 20
  .. ..$ yield   : num [1:5] 2000 3000 4000 5000 6000