Data.table inside a custom function

[fmarcondes]

Hi there,

I am new to data.table, coming from dplyr. I have the following custom function tabs:

tabs <- function(dt, x) {
tab2 <- dt[!is.na(x), ][, .(Freq = sum(nwgt0)), by = .(inc_cat, year, x)][, Prop := Freq / sum(Freq), by= .(inc_cat, year)][order(inc_cat, year)][x == 1 & !is.na(inc_cat), ] %>%
   ggplot(., aes(x= year, y = Prop, color = factor(inc_cat, levels = c(1,2,3,4),labels = c("0% to 100% FPL", "101-138% FPL", "139-200% FPL", ">200% FPL")))) +
    labs(color = "Income Categories") +
    geom_line() +
    theme_minimal() +
  ylab("Weighted proportion") +
   theme(
  panel.border = element_blank(),
  panel.grid.major = element_blank(),
  panel.grid.minor = element_blank(),
  )
return(tab2)
}

I now wish to call the function tabs . I have tried the following (does not work):

result <- hints_dt[ , tabs(.SD, x='internet_use')]

And receive the following error:

Error in `[.data.table`(dt[!is.na(x), ], , .(Freq = sum(nwgt0)), by = .(inc_cat,  : 
  The items in the 'by' or 'keyby' list are length(s) (22344,22344,1). Each must be length 22344; the same length as there are rows in x (after subsetting if i is provided).

Should be using .SDcols to specify the column internet_use. If so, how do I modify my function?

Thanks,

Felippe