drop_all_na: Drop columns for which all values are NA
In mde: Missing Data Explorer

Drop columns for which all values are NA

1	drop_all_na(df, grouping_cols = NULL)

`df`	A valid R 'object' for which the percentage of missing values is required.
`grouping_cols`	A character vector. If supplied, one can provide the columns by which to group the data.

test <- data.frame(ID= c("A","A","B","A","B"), Vals = c(rep(NA,4),2))
test2 <- data.frame(ID= c("A","A","B","A","B"), Vals = rep(NA, 5))
# drop columns where all values are NA
drop_all_na(test2)
# drop NAs only if all are NA for a given group, drops group too.
drop_all_na(test, "ID")