cross_tabulation

# Muy util para explorar diseños experimentales 

library(tidyverse)

# Agregamos algun NA
wb <- warpbreaks %>% 
  add_row(breaks= c(rep(30,5), NA), wool= rep(c("A","B"), 3), tension=rep(c("L","M", "H"), 2))

head(wb)
str(wb)

# casos completos
wb %>% 
  drop_na(breaks) %>% 
  xtabs(~ wool + tension, .) %>% 
  ftable

# en proporcion
wb %>% 
  xtabs(breaks~ wool + tension, .) %>% 
  prop.table()*100 

#sumas de valores de breaks
wb %>% 
  drop_na(breaks) %>% 
  xtabs(breaks ~ wool + tension, .) %>% 
  ftable