Set new columns "Rank" and "Index":
set.rank <==> .data$Rank = rank(.data[, .col], ties.method = 'average')
set.index <==> .data$Index = 1:nrow(.data) in a sorted data frame by .col
set.rank(.data, .col = "Read.count")
Data frame or list with data frames.
Character vector with name of the column to use for ranking or indexing.
Data frame with new column "Rank" or "Index" or list with such data frames.