Variable as a column name in data frame

Question

Is there any way to use string stored in variable as a column name in a new data frame? The expected result should be:

col.name <- \'col1\'
df <- data.fram         


        

Answer 1

You cannot pass a variable into the name of an argument like that.

Instead what you can do is:

df <- data.frame(placeholder_name = 1:4)
names(df)[names(df) == "placeholder_name"] <- col.name

or use the default name of "V1":

df <- data.frame(1:4)
names(df)[names(df) == "V1"] <- col.name

or assign by position:

df <- data.frame(1:4)
names(df)[1] <- col.name

or if you only have one column just replace the entire names attribute:

df <- data.frame(1:4)
names(df) <- col.name

There's also the set_names function in the magrittr package that you can use to do this last solution in one step:

library(magrittr)
df <- set_names(data.frame(1:4), col.name)

But set_names is just an alias for:

df <- `names<-`(data.frame(1:4), col.name)

which is part of base R. Figuring out why this expression works and makes sense will be a good exercise.