Create a vector with the value 0 instead of NULL when counting the numbers of TRUE

Question

I'd like to count the numbers of TRUE of a variable for each category of another variable. Or more precisely the average number of TRUE for each category. Afterward, I'd like to create a vector.

The code I use works fine, when the variable, like Var2 contains, both TRUE and FALSE values. However when like Var3 the variable only contains FALSE, my code creates a vector with the value of NULL. However I would like it to create a vector with the value of 0 for each category.

Any ideas?

Here is an example:

df <- data.frame(
  Var1 = c("A", "B", "A", "B", "A", "C"),
  Var2 = c(TRUE, FALSE, TRUE, FALSE, TRUE, TRUE),
  Var3 = c(FALSE, FALSE, FALSE, FALSE, FALSE, FALSE)
)
#creating some data


count1 = as.vector(tapply(df$Var1, df$Var2, table)$'TRUE')/nrow(df)
#this works fine

count2 = as.vector(tapply(df$Var1, df$Var3, table)$'TRUE')/nrow(df)
#this not. It creates only a NULL-vector

count1 works as inteded, but count2 is a NULL-vector.

Thanks!

Answer 1

Here is how to dynamically build it in base R without having to explicitly name the variables.

i1 <- as.formula(paste("cbind(", 
                       paste(setdiff(names(df), "Var1"), collapse = ", "),
                       ") ~ Var1"))
res <- aggregate(i1, df,  \(i) sum(i) / nrow(df))

res
# Var1      Var2 Var3
#1    A 0.5000000    0
#2    B 0.0000000    0
#3    C 0.1666667    0