重塑数据框-将行更改为列

Question

假设我们有一个数据框，它看起来像

set.seed(7302012)

county         <- rep(letters[1:4], each=2)
state          <- rep(LETTERS[1], times=8)
industry       <- rep(c("construction", "manufacturing"), 4)
employment     <- round(rnorm(8, 100, 50), 0)
establishments <- round(rnorm(8, 20, 5), 0)

data <- data.frame(state, county, industry, employment, establishments)

  state county      industry employment establishments
1     A      a  construction        146             19
2     A      a manufacturing        110             20
3     A      b  construction        121             10
4     A      b manufacturing         90             27
5     A      c  construction        197             18
6     A      c manufacturing         73             29
7     A      d  construction         98             30
8     A      d manufacturing        102             19

我们希望重塑它，使每一行代表一个(州和)县，而不是一个县工业，具有列construction.employment、construction.establishments和类似的制造业版本。执行此操作的有效方法是什么？

一种方法是子集

construction <- data[data$industry == "construction", ]
names(construction)[4:5] <- c("construction.employment", "construction.establishments")

对于制造业也是如此，然后进行合并。如果只有两个行业，这并不是很糟糕，但是假设有14个行业；这个过程将变得单调乏味(尽管通过在industry级别上使用for循环可以减少这种情况)。

还有其他想法吗？

Answer 1

如果我正确理解您的问题，这可以在base R重塑中完成：

reshape(data, direction="wide", idvar=c("state", "county"), timevar="industry")
#   state county employment.construction establishments.construction
# 1     A      a                     146                          19
# 3     A      b                     121                          10
# 5     A      c                     197                          18
# 7     A      d                      98                          30
#   employment.manufacturing establishments.manufacturing
# 1                      110                           20
# 3                       90                           27
# 5                       73                           29
# 7                      102                           19 

Answer 2

还可以使用重塑软件包：

library(reshape) 
m <- reshape::melt(data) 
cast(m, state + county~...) 

让步：

> cast(m, state + county~...) 
  state county construction_employment construction_establishments manufacturing_employment manufacturing_establishments
1     A      a                     146                          19                      110                           20
2     A      b                     121                          10                       90                           27
3     A      c                     197                          18                       73                           29
4     A      d                      98                          30                      102                           19

我个人使用的是基本重塑，所以我可能应该使用reshape2 (Wickham)来展示这一点，但是忘记了有一个reshape2包。略有不同：

library(reshape2) 
m <- reshape2::melt(data) 
dcast(m, state + county~...)