列表中的R子集列

Question

我有很多数据框，所以我将它们作为列表导入，但是我发现这些数据框的列数是不同的，所以我决定将它们剪掉，我只想排序列表中所有数据帧中的列1至3。

list 
[1] 
TBBA-06-5415-01A-01D-1481-05 g01023169 0.956810536587318 BSL 7 
TBBA-06-5415-01A-01D-1481-05 g03242877 0.0365834311749085 BSL 7 
TBBA-06-5415-01A-01D-1481-05 g06008330 0.0400302305964602 BSL 7 
TBBA-06-5415-01A-01D-1481-05 g08861569 0.0556296569207048 BSL 7 
TBBA-06-5415-01A-01D-1481-05 g09748749 0.183017407923698 BSL 7 
[2] 
TBBA-62-A472-01A-11D-A24I-05 g02726808 0.860054268107413 OTB 
TBBA-62-A472-01A-11D-A24I-05 g04243127 0.897393495417269 OTB 
TBBA-62-A472-01A-11D-A24I-05 g10537079 0.875143441641266 OTB 
TBBA-62-A472-01A-11D-A24I-05 g12497728 0.935925242951832 OTB 
TBBA-62-A472-01A-11D-A24I-05 g13195463 NA OTB 
[3] 
TBBA-KK-A7AV-01A-11D-A32C-05 g02442630 0.862838460053133 AS 9 133318907 
TBBA-KK-A7AV-01A-11D-A32C-05 g11045524 0.369049794350982 AS 9 133320781 
TBBA-KK-A7AV-01A-11D-A32C-05 g13597397 0.235754213039205 AS 9 133320948 
TBBA-KK-A7AV-01A-11D-A32C-05 g13835114 0.155860360642954 AS 9 133327530 
TBBA-KK-A7AV-01A-11D-A32C-05 g14010829 0.668836842295365 AS 9 
[N] 
... 

Desired output: 
[1]  
TBBA-06-5415-01A-01D-1481-05 g01023169 0.956810537 
TBBA-06-5415-01A-01D-1481-05 g03242877 0.036583431 
TBBA-06-5415-01A-01D-1481-05 g06008330 0.040030231 
TBBA-06-5415-01A-01D-1481-05 g08861569 0.055629657 
TBBA-06-5415-01A-01D-1481-05 g09748749 0.183017408 
[2]  
TBBA-62-A472-01A-11D-A24I-05 g02726808 0.860054268 
TBBA-62-A472-01A-11D-A24I-05 g04243127 0.897393495 
TBBA-62-A472-01A-11D-A24I-05 g10537079 0.875143442 
TBBA-62-A472-01A-11D-A24I-05 g12497728 0.935925243 
TBBA-62-A472-01A-11D-A24I-05 g13195463 NA 
[3]  
TBBA-KK-A7AV-01A-11D-A32C-05 g02442630 0.86283846 
TBBA-KK-A7AV-01A-11D-A32C-05 g11045524 0.369049794 
TBBA-KK-A7AV-01A-11D-A32C-05 g13597397 0.235754213 
TBBA-KK-A7AV-01A-11D-A32C-05 g13835114 0.155860361 
TBBA-KK-A7AV-01A-11D-A32C-05 g14010829 0.668836842 
[N] 
... 

我不熟悉R列表。感谢您的帮助。

Answer 1

我们可以使用lapply循环访问list并提取（[）前3列（1:3）。

lapply(lst, `[`, 1:3) 

---

如果我们从文件中读取到一个list，另一个选择是从data.table在freadselect选项，其中我们指定的列数阅读。

假设，我们要读取的工作目录下的所有文件.csv

library(data.table) 
files <- list.files(pattern = ".csv") 
lst1 <- lapply(files, fread, select = 1:3)