CODEWITHSUNDEEP
rlistaggregate
N.Varela
N.Varela

Reputation: 910

R: How to aggregate rows of dfs in a list (containing empty dfs)?

I want to aggregate all rows of data frames within a list which have the same character in a column. For this I used 

lapply(lst, function(x) aggregate(Value ~ Area, x, sum))

which works fine. However, I get also empty dfs in my list (which I need, so I cannot drop them) and I get an error:

Error in aggregate.data.frame(mf[1L], mf[-1L], FUN = FUN, ...) : 
  no rows to aggregate

Is there a way to overcome this error? Thanks. Below a small example:

lst <- list("111.2012"=data.frame("Area"=character(0), "Value"=numeric(0)),
            "112.2012"=data.frame("Area"=c("a","b","b","a"), "Value"=c(1,5,3,2)))

Upvotes: 1

Views: 182

Answers (1)

Eli Korvigo
Eli Korvigo

Reputation: 10513

lst <- list("111.2012"=data.frame("Area"=character(0), "Value"=numeric(0)),
            "112.2012"=data.frame("Area"=c("a","b","b","a"), "Value"=c(1,5,3,2)))


lapply(lst, function(x) if (nrow(x)) aggregate(Value ~ Area, x, sum) else x)

Output

$`111.2012`
[1] Area  Value
<0 rows> (or 0-length row.names)

$`112.2012`
  Area Value
1    a     3
2    b     8

Upvotes: 3

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