Since data.table includes the awesome fread function which supports sep2 for lists within cells I was completely shocked to find there is no way to write a data.table with lists in columns to a delimited text file.

I had to roll my own function to save my data.tables but its not very generic.

write.data.table <- function(x, file) {
  fileConn <-file(file)
  writeLines(c(paste(colnames(x),collapse="\t"),
               x[,paste(id,parent,layer,start,end,sapply(x,function(o) paste(o,collapse=",")),sapply(y,function(o) paste(o,collapse=",")),sep="\t")]
  ), fileConn)
  close(fileConn)
}

There has to be a better way.