Aggregating all unique values of each column of data frame

Question

I have a large data frame (1616610 rows, 255 columns) and I need to paste together the unique values of each column based on a key.

For example:

>         


        

Answer 1

You could do the following with dplyr

func_paste <- function(x) paste(unique(x), collapse = ', ')
data %>%
    group_by(a) %>%
    summarise_each(funs(func_paste))

##      a               b      c                  d
##  (dbl)           (chr)  (chr)              (chr)
##1     1 apples, oranges 12, 22             Monday
##2     2          apples 45, 67 Tuesday, Wednesday
##3     3      grapefruit     28            Tuesday

Answer 2

Moved from comments:

library(data.table)

dt <- as.data.table(data)
dt[, lapply(.SD, function(x) toString(unique(x))), by = a]

giving:

   a               b      c                  d
1: 1 apples, oranges 12, 22             Monday
2: 2          apples 45, 67 Tuesday, Wednesday
3: 3      grapefruit     28            Tuesday