在dcast中订购列

Question

在使用dcast时，如何基于列'Col'指定列顺序？

df <- dcast(x, ID ~ ColumnName, value.var = "Answer")

我需要解决方案不特定于数据，因为x可以是任何问题的结果（因此Col可以是1-3或1-2等）。下面是x的两个虚拟示例。

ID        Answer        ColumnName        Col
1         Anduin        First Name        1
1         Wrynn         Surname           2
1         Alliance      Faction           3
2         Sylvanas      First Name        1
2         Windrunner    Surname           2
2         Horde         Faction           3



ID        Answer        ColumnName        Col
1         The Kirin Tor Quest             1
1         90            Level             2
2         Emissary      Quest             1
2         38            Level             2

Answer 1

我没有看到dcast参数可以指定列的最终顺序，但是始终可以将结果子集化。

fun_dcast <- function(DF, formula = ID ~ ColumnName, value.var = "Answer"){
  reshape2::dcast(DF, formula, value.var = value.var)[c(1, 1 + unique(DF[["Col"]]))]
}

fun_dcast(x1)
#  ID  Faction First Name    Surname
#1  1 Alliance     Anduin      Wrynn
#2  2    Horde   Sylvanas Windrunner

fun_dcast(x2)
#  ID Level         Quest
#1  1    90 The Kirin Tor
#2  2    38      Emissary

数据。

x1 <- read.table(text = "
ID        Answer        ColumnName        Col
1         Anduin        'First Name'        1
1         Wrynn         Surname           2
1         Alliance      Faction           3
2         Sylvanas      'First Name'        1
2         Windrunner    Surname           2
2         Horde         Faction           3
", header = TRUE)


x2 <- read.table(text = "
ID        Answer        ColumnName        Col
1         'The Kirin Tor' Quest             1
1         90            Level             2
2         Emissary      Quest             1
2         38            Level             2
", header = TRUE)

Answer 2

pickle和help("dcast", "reshape2")中都没有很好的文档记录，但是如果help("dcast", "data.table")是一个因数，则这些列按因数级别排序。

没有ColumnName

各列按字母顺序排列，与factor()

中指定的顺序不一致

Col

# create sample dataset
x <- readr::read_table(
"ID        Answer        ColumnName        Col
1         Anduin        First Name        1
1         Wrynn         Surname           2
1         Alliance      Faction           3
2         Sylvanas      First Name        1
2         Windrunner    Surname           2
2         Horde         Faction           3")

reshape2::dcast(x, ID ~ ColumnName, value.var = "Answer")

使用 ID Faction First Name Surname 1 1 Alliance Anduin Wrynn 2 2 Horde Sylvanas Windrunner 和factor()

这些列按从reorder()得出的因子水平进行排序

Col

library(magrittr)   # not essential; just used to improve readabilty
x$ColumnName <- with(x, factor(ColumnName, levels = unique(ColumnName)) %>% reorder(Col))
reshape2::dcast(x, ID ~ ColumnName, value.var = "Answer")