What does 'col.names' do in 'as.data.frame' in R? [duplicate]

Question

I'm using as.data.frame() function to turn a table into dataframe in R, and I would like to set column names with the function.

I found that there's an optional argument for as.data.frame(), which is col.names.

The documentation says that it's a character vector of column names. However, whatever I put in col.names, the result keeps the same.

x = c('a','b','c','a')
x_table = table(x)
x_df = as.data.frame(x_table, col.names = c('name', 'freq'))

Output here is:

    x Freq
1   a    2
2   b    1
3   c    1

I understand I could use colnames(df) to change the column names after the dataframe is created, but I really wonder why col.names does not work here.

Thank you.

Answer 1

If you want to avoid assigning the column names after creating the dataframe, you can utilize the dnn parameter in the table function to specify your "name" column, and the responseName parameter in the as.data.frame function to specify the "freq" column.

x <- c('a','b','c','a')
x_df <- as.data.frame(table(x, dnn = list("name")), responseName = "freq")