r - R Organize data in a list

Question

I have a data set that I'd like to organize into a list but am unsure of the most efficient way to do so. It's a list of sales people and products sold:

  rowId       repNum       prodNum
   001         12006        335506883
   002         12008        152348345
   003         12055        993047386
   004         12006        294726636
   005         12069        110847537
   006         12006        335506883
   007         12006        152348345
   ...           ...           ...

I'd like to create a list where each element contains a vector of items that rep has sold, my initial idea was to use tapply but that needs a function to net by. Any other suggestions?

Answer 1

If your data.frame is called dataset,

split(dataset, dataset$repNum)

will create a list with a component for each repNum

---

> split(dataset, dataset$repNum)
$`12006`
  rowId repNum   prodNum
1     1  12006 335506883
4     4  12006 294726636
6     6  12006 335506883
7     7  12006 152348345

$`12008`
  rowId repNum   prodNum
2     2  12008 152348345

$`12055`
  rowId repNum   prodNum
3     3  12055 993047386

$`12069`
  rowId repNum   prodNum
5     5  12069 110847537

---

As pointed out by mrdwab, you can get "vector[s] of items that rep has sold" by splitting the prodNum like this:

> split(dataset$prodNum, dataset$repNum)
$`12006`
[1] 335506883 294726636 335506883 152348345

$`12008`
[1] 152348345

$`12055`
[1] 993047386

$`12069`
[1] 110847537

Answer 2

Using tapply(), you can do it like this:

with(dataset, tapply(prodNum, repNum, FUN=function(X) X))
# $`12006`
# [1] 335506883 294726636 335506883 152348345
# 
# $`12008`
# [1] 152348345
# 
# $`12055`
# [1] 993047386
# 
# $`12069`
# [1] 110847537

Answer 3

You could also use dlply from plyr:

require(plyr) ## install.packages("plyr") if you haven't already
dlply(dataset,"repNum",function(x) return(x$prodNum))
#$`12006`
#[1] 335506883 294726636 335506883 152348345
#
#$`12008`
#[1] 152348345
#
#$`12055`
#[1] 993047386
#
#$`12069`
#[1] 110847537