http://stackoverflow.com/questions/18484243/r-regex-from-string-to-two-dimensional-data-frame-in-one-command iterate over each row and split it numerical values into the columns named by the key. Example of few rows showing, how I would like it will looks like:

gistfile1.r

df <- data.frame(m = c(
  "{'#JJ': 121, '#NN': 938, '#DT': 184, '#VB': 338, '#RB': 52}",
  "{'#NN': 168, '#DT': 59, '#VB': 71, '#RB': 5, '#JJ': 35}",
  "{'#JJ': 18, '#NN': 100, '#DT': 23, '#VB': 52, '#RB': 11}"
))
 
parse.one <- function(s) {
  require(rjson)
  y <- fromJSON(gsub("'", '"', s))
  names(y) <- gsub("#", "", names(y))
  as.data.frame(y)
}
 
library(plyr)
rbind.fill(lapply(df$m, parse.one))

#    JJ  NN  DT  VB RB
# 1 121 938 184 338 52
# 2  35 168  59  71  5
# 3  18 100  23  52 11