将 strsplit 的结果分配给数据框的多列

Question

我正在尝试将一个字符向量拆分为三个不同的向量，在一个数据框中。

我的数据是这样的：

> df <- data.frame(filename = c("Author1 (2010) Title of paper", 
                                "Author2 et al (2009) Title of paper",
                                "Author3 & Author4 (2004) Title of paper"),
                   stringsAsFactors = FALSE)

我想将这 3 个信息（authors、year、title）分成三个不同的列，这样它会是：

> df
                          filename             author  year   title
 1           Author1 (2010) Title1            Author1  2010  Title1
 2     Author2 et al (2009) Title2      Author2 et al  2009  Title2
 3 Author3 & Author4 (2004) Title3  Author3 & Author4  2004  Title3

我使用strsplit 将每个filename 拆分为3 个元素的向量：

 df$temp <- strsplit(df$filename, " \\(|\\) ")

但现在，我找不到将每个元素放在单独列中的方法。我可以访问这样的特定信息：

> df$temp[[2]][1]
[1] "Author2 et al"

但找不到如何将其放在其他列中

> df$author <- df$temp[[]][1]
Error

Answer 1

你可以从data.table的开发版试试tstrsplit

library(data.table)#v1.9.5+
 setDT(df)[, c('author', 'year', 'title') :=tstrsplit(filename, ' \\(|\\) ')]
df
#                                  filename             author year
#1:           Author1 (2010) Title of paper           Author1  2010
#2:     Author2 et al (2009) Title of paper     Author2 et al  2009
#3: Author3 & Author4 (2004) Title of paper Author3 & Author4  2004
#             title
#1:  Title of paper
#2:  Title of paper
#3:  Title of paper

编辑：包含 OP 的拆分模式以删除空格。

Answer 2

使用tidyr 包，这里有一个separate 解决方案：

separate(df, "filename", c("Author","Year","Title"), sep=" \\(|\\) "), remove=F)
#                                  filename            Author
# 1           Author1 (2010) Title of paper           Author1
# 2     Author2 et al (2009) Title of paper     Author2 et al
# 3 Author3 & Author4 (2004) Title of paper Author3 & Author4
#   Year          Title
# 1 2010 Title of paper
# 2 2009 Title of paper
# 3 2004 Title of paper

前导空格和尾随空格都已计算在内

Answer 3

result <- cbind(df, do.call("rbind", strsplit(df$filename, " \\(|\\) ")))
colnames(result)[2:4] <- c("author", "year", "title")

Answer 4

数据帧有一个基本的t-方法（转置）：

 res <- t( data.frame(  strsplit(df$filename, " \\(|\\) ") ))
 colnames(res) <- c("author", "year", "title")
 rownames(res) <- seq_along(rownames(res) )
 res
#--------------
  author              year   title           
1 "Author1"           "2010" "Title of paper"
2 "Author2 et al"     "2009" "Title of paper"
3 "Author3 & Author4" "2004" "Title of paper"