filter one column by two conditions (one value and empty cell) in R

Question

I'd like to filter a column wherein value is 0 or value has no data. I've tried the following lines but neither seems to be doing what I want.

# demo2122 = dataframe 
# grp_mlk = column 

demo2122 %>% filter(grp_mlk == 0 | grp_mlk == "")
demo2122 %>% filter(grp_mlk == 0 | grp_mlk == NA)

Thanks in advance for your help!

akrun · Answer

Instead of grp_mlk == NA, use is.na(grp_mlk) as by default filter removes the NA rows

library(dplyr)
demo2122 %>%
    filter(grp_mlk == 0| is.na(grp_mlk))