r - 分割字符串并转换为数据框

Question

我有一个 65k 元素的字符向量，格式为.每个元素的长度不同，但范围从 3 到 8(基于逗号):

b[1]= "aaaa, bbbb, cccc"
...
b[1000]="aaaa, bbbb, cccc, dddd, eeee, ffff"
...
b[3000]="aaaa, bbbb, cccc, dddd, eeee, ffff, gggg"
b[3001]="aaaa, bbbb, cccc"

我想转换为数据框:

row  col1 col2 col3 col4 col5 col6 col7
1    aaaa bbbb cccc
1000 aaaa bbbb cccc dddd eeee ffff
3000 aaaa bbbb cccc dddd eeee ffff gggg

我尝试过:

 data.frame( do.call( rbind, strsplit( b, ',' ) ) ) 

得到:

Warning message: In (function (..., deparse.level = 1) : number of columns of result is not a multiple of vector length (arg 1)

有什么建议吗？

Answer 1

将字符串粘贴在一起并用 "\n" 折叠后，我们可以使用 read.csv。

read.csv(text = paste0(b, collapse = "\n"), header = FALSE)

#    V1    V2    V3    V4    V5    V6    V7
#1 aaaa  bbbb  cccc                        
#2 aaaa  bbbb  cccc  dddd  eeee  ffff      
#3 aaaa  bbbb  cccc  dddd  eeee  ffff  gggg

如果您想将空字符串读取为NA，请在na.strings中指定它们

read.csv(text = paste0(b, collapse = "\n"), header = FALSE, na.strings = "")

---

另一个选项是来自stringi的stri_list2matrix

data.frame(stringi::stri_list2matrix(strsplit(b, ","), byrow = TRUE))

#   X1    X2    X3    X4    X5    X6    X7
#1 aaaa  bbbb  cccc  <NA>  <NA>  <NA>  <NA>
#2 aaaa  bbbb  cccc  dddd  eeee  ffff  <NA>
#3 aaaa  bbbb  cccc  dddd  eeee  ffff  gggg

数据

b <- c("aaaa, bbbb, cccc", "aaaa, bbbb, cccc, dddd, eeee, ffff", 
       "aaaa, bbbb, cccc, dddd, eeee, ffff, gggg")