Get the number of factor levels from columns inside a function in R

Question

I am trying to create a function that performs several statistical tests for specific columns in a data framework. Some of the tests require more than one level. I would like to check how many levels are in a particular column, but cannot seem to be correct.

In my actual code, this section will be followed by ifelse, which returns a string saying "only one level" if it is single, or continues the statistical test if> 1.

require("dplyr")
df <- data.frame(A = c("a", "b", "c"), B = c("a", "a", "a"), C = c("a", "b", "b")) %>%
    mutate(A = factor(A)) %>%
    mutate(B = factor(B)) %>%
    mutate(C = factor(C))

my_funct <- function(data_f, column){

    n_fact <- paste("data_f", column, sep = "$")

    n_levels <- do.call("nlevels",
                        list(x = as.name(n_fact)))
    print(n_levels)
}

`` ``

Then I call my function using dataframe and column

my_funct(df, "A")

I get the following error: Error in levels (x): object 'data_f $ A' not found

If I remove the as.name () wrapper, it will return the value 0.

Answer 1

, , , data_f$A - , .

. . , , [[. , :

nlevels(data_f[[column]])

:

sapply(data_f, nlevels)