
      library(foreign)
      library(dplyr)
      data_URL <- "https://github.com/Jeshua-Romero-Guadarrama/Econoalgoritmia/tree/main/data/fastfood.dta?raw=true"
      dat <- read.dta(data_URL)
      dat <- dat %>% 
        mutate(FTE = nmgrs + empft + (0.5 * emppt),
        FTE2 = nmgrs2 + empft2 + (0.5 * emppt2))


      # generar los subconjuntos
      
      # calcular las medias de grupo


      # generar los subconjuntos
      dat_NJ <- subset(dat, state == 1)
      dat_PA <- subset(dat, state == 0)
           
      # calcular las medias de grupo
      dat %>% 
      group_by(state) %>% 
      summarise(mean(FTE, na.rm = T),
      mean(FTE2, na.rm = T))


      ex() %>% check_predefined_objects("dat")
      ex() %>% check_object("dat_NJ") %>% check_equal(undefined_msg = "No ha definido `dat_NJ`!")
      ex() %>% check_object("dat_PA") %>% check_equal(undefined_msg = "No ha definido `dat_NJ`!")   
      ex() %>% check_or(
        ex() %>% check_output_expr("dat %>% 
        group_by(state) %>% 
        summarise(mean(FTE, na.rm = T),
        mean(FTE2, na.rm = T))", missing_msg = "Parece que no todos las medias de grupo se han impreso correctamente en la consola."),
        ex() %>% check_output_expr("mean(dat_NJ$FTE, na.rm=T);mean(dat_NJ$FTE2, na.rm = T);mean(dat_PA$FTE, na.rm = T);mean(dat_PA$FTE2, na.rm = T)", missing_msg = "Parece que no todos las medias de grupo se han impreso correctamente en la consola.")
      )
      success_msg(msg = "¡Correcto!")