将R中的JSON读取到data.frame

Question

I have list of JSON values (actually it's a text file where every line is one JSON object). Like this:

{ "id": 1, "name": "john", "age": 18, "education": "master" }
{ "id": 2, "name": "jack", "job": "clerk" }
...

Some of the values can be missing (eg first item doesn't have "job" value and second item doesn't have "education" and "age").

I need to create data frame in R and fill all missing column values as NAs (if field with unique name exists in at least one row). How to achieve this easier?

What I already done - I installed "rjson" package and parsed these lines to R lists. Let's assume that lines variable is a character vector of lines.

library(rjson)
lines <- // initialize "lines" var here
jsons <- sapply(lines, fromJSON)

"jsons" variable became "list of lists" (every JSON object is converted to list in R terminology). How to convert it to data.frame?

I want to see the following data frame for the example I provided:

"id" | "name" | "age" | "education" | "job"
-------------------------------------------
1    | "john" |  18   |  "master"   |   NA
2    | "jack  |  NA   |     NA      | "clerk"

Answer 1

From plyr you can use rbind.fill to add the NAs for you

library(plyr)
rbind.fill(sapply(jsons, data.frame), jsons)

#   id name age education   job
# 1  1 john  18    master  <NA>
# 2  2 jack  NA      <NA> clerk

or from data.table

library(data.table)
rbindlist(jsons, fill=T)

and dplyr

library(dplyr)
bind_rows(sapply(jsons, data.frame))

Answer 2

Future me, correcting past me's mistakes. It would make more sense to use jsonlite 's stream_in

stream_in(txtfile)

# To test on `txt` from below, try:
# stream_in(textConnection(txt))

# Found 2 records...
# Imported 2 records. Simplifying...
#  id name age education   job
#1 NA john  18    master  <NA>
#2  2 jack  NA      <NA> clerk

---

Use the jsonlite package's fromJSON function, after making a few inline edits to your original text data (I've also edited the first piece of id data to include an explicit null value, to show that it deals with this):

fromJSON(paste0("[", gsub("}\n", "},\n", txt), "]"))
#  id name age education   job
#1 NA john  18    master  <NA>
#2  2 jack  NA      <NA> clerk

All I did was add a little formatting to wrap all the JSON lines together in [ and ] and add a comma at the end of each closing } - resulting in an output like the below which can be processed all at once by jsonlite::fromJSON :

[{"1":"one"},{"2":"two"}]

Where txt was your lines of data as presented, with a null in the id variable:

txt <- "{ \"id\": null, \"name\": \"john\", \"age\": 18, \"education\": \"master\" }
{ \"id\": 2, \"name\": \"jack\", \"job\": \"clerk\" }"