Merge multiple data tables with duplicate column names

Question

I am trying to merge (join) multiple data tables (obtained with fread from 5 csv files) to form a single data table. I get an error when I try to merge 5 data tables, but wo

Answer 1

Here's a way of keeping a counter within Reduce, if you want to rename during the merge:

Reduce((function() {counter = 0
                    function(x, y) {
                      counter <<- counter + 1
                      d = merge(x, y, all = T, by = 'x')
                      setnames(d, c(head(names(d), -1), paste0('y.', counter)))
                    }})(), list(DT1, DT2, DT3, DT4, DT5))
#   x y.x y.1 y.2 y.3 y.4
#1: a  10  11  12  13  14
#2: b  11  12  13  14  15
#3: c  12  13  14  15  16
#4: d  13  14  15  16  17
#5: e  14  15  16  17  18
#6: f  15  16  17  18  19