Function to count NA values at each level of a factor

Question

I have this dataframe:

set.seed(50)
data <- data.frame(age=c(rep(\"juv\", 10), rep(\"ad\", 10)),
                   sex=c(rep(\"m\", 10), rep(\"f\", 10)),         


        

Answer 1

Looking for something like this...???

library(doBy)
summaryBy(length+width+height~age+sex+size,
          data=data,
          FUN=function(x) sum(is.na(x)),
          keep.names=TRUE)
  age sex  size length width height
1  ad   f small      3     4      4
2 juv   m large      5     4      4