Aggregate data frame while keeping original order, in a simple manner

Question

I\'m having some trouble aggregating a data frame while keeping the groups in their original order (order based on first appearance in data frame). I\'ve managed to get it right

Answer 1

A bit tough to read, but it gives you what you want and I added some comments to clarify.

# Define the columns you want to combine into the grouping variable
sel.col <- grepl("^sel", names(orig.df))
# Create the grouping variable
lev <- apply(orig.df[sel.col], 1, paste, collapse=" ")
# Split and sum up
data.frame(unique(orig.df[sel.col]),
           t(sapply(split(orig.df[!sel.col], factor(lev, levels=unique(lev))),
                    apply, 2, sum)))

The output looks like this

   sel.1 sel.2 add.1 add.2
1      5     4    96    84
2      2     2   175   176
3      1     5   384   366
5      2     5    95    89
6      4     1   174   192
7      2     4    82    87
8      5     3    91    98
10     3     2   189   178
11     1     4   170   183
14     1     1   100    91
17     3     3    81    82
19     5     5    83    88
20     2     3    90    96