When coding in R, how do you get the summary statistic when the data is categorized? For example, I'm trying to get the mean of race/ethnicity for a group of women in the placebo and in the treatment. For age I was able to use tapply(mat_age,treatment,summary) because it's age in years.

For race/ethnicitycit is: race_ethnicity Mother's self-reported race/ethnicity (B=black, H=Hispanic, W=white) and when I try the same, I get this.

tapply(race_ethnicity,treatment,summary)

$`0`

LengthClassMode

200 character character

$`1`

LengthClassMode

200 character character

I need to know the mean and sd for the race/ethnicity for women in the placebo group and women in the treatment group but I don't know the R coding to get there.