使用字符串中的列名初始化R data.table

Question

I want to do something like this:

> colname <- "a"
> dt <- data.table(colname = c(1,2,3,4))
   a
1: 1
2: 2
3: 3
4: 4

But instead, I get this:

> colname <- "a"
> dt <- data.table(colname = c(1,2,3,4))
   colname
1:       1
2:       2
3:       3
4:       4

Is there a good way around this besides creating the data.table and assigning the names afterward?

Answer 1

We can use setnames . The advantage of setnames is it can be used to name either all the columns or a subset of columns by providing the names in the old and new argument

dt <- data.table(c(1,2,3,4))
setnames(dt, colname)

---

We can wrap setnames while creating the object itself

dt <- setnames(data.table(c(1,2,3,4)), colname)[]
dt
#   a
#1: 1
#2: 2
#3: 3
#4: 4

Answer 2

Another way to do so without using data.table is using the base function names

> colnames <- "a"
> dt <- data.table(c(1,2,3,4))
> dt
   V1
1:  1
2:  2
3:  3
4:  4
> names(dt) <- colnames
> dt
   a
1: 1
2: 2
3: 3
4: 4

If you have a data frame with multiple columns, just pass the vector of column names to the function names .