I am using levels(dataset$variable) and it is still showing a NULL output-CodePudding

This is all using R in Rstudio. I am hoping for an quick solution. I am currently running through a Udacity R course, and they are asking me to run the below code to show the levels for the variable age.range in a dataset called reddit:

levels(reddit$age.range)

However, it keeps returning with the same output.

NULL

In their video tutorial with the same data set it seems to be working fine, and showing a clear series of levels for this variable, so I really don't understand what the issue is. Please help.

> str(reddit)
'data.frame':   32754 obs. of  14 variables:
 $ id               : int  1 2 3 4 5 6 7 8 9 10 ...
 $ gender           : int  0 0 1 0 1 0 0 0 0 0 ...
 $ age.range        : chr  "25-34" "25-34" "18-24" "25-34" ...
 $ marital.status   : chr  NA NA NA NA ...
 $ employment.status: chr  "Employed full time" "Employed full time" "Freelance" "Freelance" ...
 $ military.service : chr  NA NA NA NA ...
 $ children         : chr  "No" "No" "No" "No" ...
 $ education        : chr  "Bachelor's degree" "Bachelor's degree" "Some college" "Bachelor's degree" ...
 $ country          : chr  "United States" "United States" "United States" "United States" ...
 $ state            : chr  "New York" "New York" "Virginia" "New York" ...
 $ income.range     : chr  "$150,000 or more" "$150,000 or more" "Under $20,000" "$150,000 or more" ...
 $ fav.reddit       : chr  "getmotivated" "gaming" "snackexchange" "spacedicks" ...
 $ dog.cat          : chr  NA NA NA NA ...
 $ cheese           : chr  NA NA NA NA ...

> table(reddit$age.range)

      18-24       25-34       35-44       45-54       55-64 65 or Above    Under 18 
      15802       11575        2257         502         140          60        2330

CodePudding user response：

The problem here seems to be that the variable is of type character. For levels() to work, it needs to be a factor. So this should work:

reddit$age.range <- as.factor(reddit$age.range)
levels(reddit$age.range)

The reason for this problem might be that you imported these data using read.csv or read.table, with the option stringsAsFactors = FALSE. The default value for this changed fairly recently. It's a good idea to always specify this option explicitly when loading data.

CodePudding user response：

I’m guessing the course you’re following was created before R 4.0. In R4 the default value for the “stringsAsFactors” argument to data.frame was changed from true to false.