List of lists to dataframe in R

Question

I have to cope with an ugly list called ul that looks like this:

[[1]]
[[1]]$param
     name     value 
"Section"       "1" 

[[1]]$param
   name   value 
"field"     "1" 

[[1]]$param
          name          value 
"final answer"            "1" 

[[1]]$param
    name    value 
"points"   "-0.0" 


[[2]]
[[2]]$param
     name     value 
"Section"       "1" 

[[2]]$param
   name   value 
"field"     "2" 

[[2]]$param
          name          value 
"final answer"            "1" 

[[2]]$param
    name    value 
"points"    "1.0" 


[[3]]
[[3]]$param
     name     value 
"Section"       "1" 

[[3]]$param
   name   value 
"field"     "3" 

[[3]]$param
          name          value 
"final answer"        "0.611" 

[[3]]$param
    name    value 
"points"    "1.0" 

I would like to convert the list to a simple data frame, i.e.

Section    field    final answer    points
      1        1               1      -0.0
      1        2               1       1.0
      1        3           0.611       1.0

Is there any straightforward way to achieve that? or do I have to make a function accessing each list individually and binding it to a dataframe?

The data is imported from an uglier xml file, so if someone wants to play with it there is a link to the RData file. Sorry for not having reproducible code. Thank you very much.

Answer 1

There is probably a better solution, but this should get you started. First, we load some libraries

R> library(plyr)
R> library(reshape2)

Then handle your lists in two parts.

##lapply applies ldply to each list element in turn
ul1 = lapply(ul, ldply)

##We then do the same again
dd = ldply(ul1)[,2:3]

Next we label output according to their list order

R> dd$num = rep(1:3, each=4)

Then we convert from long to wide format

R> dcast(dd, num ~ name)

  num field final answer points Section
1   1     1            1   -0.0       1
2   2     2            1    1.0       1
3   3     3        0.611    1.0       1

Answer 2

An answer to a similar problem was given by Marc Schwartz at this link : https://stat.ethz.ch/pipermail/r-help/2006-August/111368.html

I'm copying it in case the link is deleted.

 as.data.frame(sapply(a, rbind))

   V1 V2 V3
1  a  b  c
2  1  3  5
3  2  4  6

or:

as.data.frame(t(sapply(a, rbind)))
   V1 V2 V3
1  a  1  2
2  b  3  4
3  c  5  6