Extracting specific columns from a data frame

2018-06-25 07:52:05

I have an R data frame with 6 columns, and I want to create a new dataframe that only has three of the columns.

Assuming my data frame is df , and I want to extract columns A , B , and E , this is the only command I can figure out:

 data.frame(df$A,df$B,df$E)

Is there a more compact way of doing this?

就在这里。

# data for reproducible example
# (and to avoid confusion from trying to subset `stats::df`)
df <- setNames(data.frame(as.list(1:5)), LETTERS[1:5])
# subset
df[,c("A","B","E")]

这是subset()函数的作用：

> dat <- data.frame(A=c(1,2),B=c(3,4),C=c(5,6),D=c(7,7),E=c(8,8),F=c(9,9)) 
> subset(dat, select=c("A", "B"))
  A B
1 1 3
2 2 4

There are two obvious choices: Joshua Ulrich's df[,c("A","B","E")] or

df[,c(1,2,5)]

as in

> df <- data.frame(A=c(1,2),B=c(3,4),C=c(5,6),D=c(7,7),E=c(8,8),F=c(9,9)) 
> df
  A B C D E F
1 1 3 5 7 8 9
2 2 4 6 7 8 9
> df[,c(1,2,5)]
  A B E
1 1 3 8
2 2 4 8
> df[,c("A","B","E")]
  A B E
1 1 3 8
2 2 4 8

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