如何在 R 中引用带有字符串的数据框元素？

Question

n <- 1
sn <- "n"
get (sn)

This will work. However, the following won't work:

n <- as.data.frame(matrix(1,2,2))
sn <- "n$V1"
get (sn)

How should I make this work?

eval(parse(text=sn))

works. Thanks.

I am doing that because there are 1000 variables in the dataframe and I need a variable passed from a function to tell which variable out of the 1000 variables that I need to work further on.

Answer 1

You almost certainly want to pass just the name of the column within the data frame, then use [[ -indexing to retrieve the vector you want:

n <- as.data.frame(matrix(1,2,2))
sn <- "V1"
n[[sn]]
## [1] 1 1