Aggregating by unique identifier and concatenating related values into a string [duplicate]

Answer 1

Here's the information in base R:

myby <- by(df$id,df$brand,function(x)paste(x,collapse=","))

The formatting of "by" objects is weird. You can take data.frame(id=c(myby)) and the brands will become rownames:

#                                    id
# RadioShack                       2308
# Rag & Bone                       4466
# Ragu                        1830,4518
# Ralph Lauren 1638,2719,2720,2721,2722

Alternately, if you load the data.table package, this will work:

dt <- data.table(df)
dt[,paste(id,collapse=","),by=brand]
#           brand                       V1
# 1:   RadioShack                     2308
# 2:   Rag & Bone                     4466
# 3:         Ragu                1830,4518
# 4: Ralph Lauren 1638,2719,2720,2721,2722