Extracting outputs from lapply to a dataframe

Question

I have some R code which performs some data extraction operation on all files in the current directory, using the following code:

files <- list.files(\".\         


        

Answer 1

One option might be to use the ldply function from the plyr package, which will stitch things back into a data frame for you.

A trivial example of it's use:

ldply(1:10,.fun = function(x){c(runif(1),"a")})
                    V1 V2
1    0.406373084755614  a
2    0.456838687881827  a
3    0.681300171650946  a
4    0.294320539338514  a
5    0.811559669673443  a
6    0.340881009353325  a
7    0.134072444401681  a
8  0.00850683846510947  a
9    0.326008745934814  a
10    0.90791508089751  a

But note that if you're mixing variable types with c(), you probably will want to alter your function to return simply data.frame(name= name,value = value) instead of c(name,value). Otherwise everything will be coerced to character (as it is in my example above).

Answer 2

inp <- list(c("amer", "14.5"), c("appl", "14.2"), .... # did not see need to copy all

data.frame( first= sapply( inp, "[", 1), 
            second =as.numeric( sapply( inp, "[", 2) ) )

   first second
1   amer   14.5
2   appl   14.2
3   brec   13.1
4   camb   13.5
5   camo   30.1
6   cari   13.8
snipped output

Answer 3

Try this if results were your list:

> as.data.frame(do.call(rbind, results))

     V1   V2
1  amer 14.5
2  appl 14.2
3  brec 13.1
4  camb 13.5
...

Answer 4

Because and forNelton took the response I was in the process of giving and Joran took the only other reasonable response I could think of and since I'm supposed to be writing a paper here's a ridiculous answer:

#I named your list LIST
LIST2 <-  LIST[[1]]
lapply(2:length(LIST), function(i) {LIST2 <<- rbind(LIST2, LIST[[i]])})
data.frame(LIST2)