Sort key so that non missing values are first in the value vector.
naLast(key, byvar = "name_new", valvar = "value_new",
na.strings = c("\\.", "", "\\s+", "N/A"))
key, long or wide
Default is "name_new", the column for sorting into blocks.
The value variable on which sorting is to be done, "value_new".
vector of characters to be treated as NA
sorted key, with blocks that have the missings last