ldply with subset does not see local variable

Question

i have a list of team names (teamNames) and a list of data frames (weekSummaries)

i want to get a list of team summaries by week:

teamSummaries <- llply(teamNames,getTeamSubset)

getTeamSubset = function(teamName){
  temp=ldply(weekSummaries,subset,team_name==teamName)
}

however, when i run this i get an error

>Error in eval(expr, envir, enclos) : object 'teamName' not found

but when i run the command

>ldply(weekSummaries,subset,team_name=="Denver Broncos")

i get a data frame with the information i need for one team... can somebody point out what i'm doing wrong?

See http://adv-r.had.co.nz/Computing-on-the-language.html and http://stackoverflow.com/questions/9860090/in-r-why-is-better-than-subset. — mnel, Dec 17 '13 at 22:48
thanks @mnel. from looking at those links, it looks like subset works within the scope of the data_frame it is passed. i couldn't seem to sort out how to fix it with eval. i'm posting an alternate solution that uses a custom function, thus avoiding subset altogether. — dance, Dec 18 '13 at 02:14

score 0 · Accepted Answer · answered Dec 18 '13 at 02:16

Looks like the answer is not to use the subset function, and instead to use a custom function, passing it the data frame, then subsetting using bracket notation. such as this:

teamSummaries <- llply(teamNames,getTeamSubset)

getTeamSubset = function(teamName){
  temp=ldply(weekSummaries,function(week){
    week[week$team_name==teamName,]
  })
}

ldply with subset does not see local variable

1 Answers1