Simple formatting with tidyjson with R - json

Question

I have a simple JSON file which I'm attempting to coerce into an R data.frame.
json = "
{ \"objects\":
{
\"object_one\": {
\"key1\" : \"value1\",
\"key2\" : \"value2\",
\"key3\" : \"0\",
\"key4\" : \"value3\",
\"key5\" : \"False\",
\"key6\" : \"False\"
},
\"object_two\": {
\"key1\" : \"0.5\",
\"key2\" : \"0\",
\"key3\" : \"343\",
\"key4\" : \"value4\",
\"key5\" : \"True\",
\"key6\" : \"True\"
}
}
}
"
and I simply want to extract the name of each object as a index key (or rowname), create column names from the keys and spread the values.
Unfortunately I've had no luck unpicking the syntax. Can anyone help?
Thanks
Stuart

Answer 1

There are two ways to do this with tidyjson, the first is to use tidyjson::append_values_string and then tidyr::spread:
library(tidyjson)
library(dplyr)
library(tidyr)
json %>%
enter_object("objects") %>%
gather_keys("object") %>%
gather_keys("key") %>%
append_values_string("value") %>%
tbl_df %>% spread(key, value)
#> # A tibble: 2 x 8
#> document.id object key1 key2 key3 key4 key5 key6
#> * <int> <chr> <chr> <chr> <chr> <chr> <chr> <chr>
#> 1 1 object_one value1 value2 0 value3 False False
#> 2 1 object_two 0.5 0 343 value4 True True
The other way is to use tidyjson::spread_values to specific each key separately:
json %>%
enter_object("objects") %>%
gather_keys("object") %>%
spread_values(
key1 = jstring("key1"),
key2 = jstring("key2"),
key3 = jnumber("key3"),
key4 = jstring("key4"),
key5 = jstring("key5"),
key6 = jstring("key6")
)
#> document.id object key1 key2 key3 key4 key5 key6
#> 1 1 object_one value1 value2 0 value3 False False
#> 2 1 object_two 0.5 0 343 value4 True True
The advantage of the second approach is that you can (a) specify the types of each column and (b) will be guaranteed to get the same data.frame structure even if the keys change (or are missing) in some documents or objects.

Answer 2

Not entirely sure on your desired output, but you can use jsonlite::fromJSON to extract the data, and data.table::rbindlist to put it into a data.table
library(jsonlite)
library(data.table)
rbindlist(fromJSON(json))
# object_one object_two
# 1: value1 0.5
# 2: value2 0
# 3: 0 343
# 4: value3 value4
# 5: False True
# 6: False True
Based on your comment, another approach that involves some reshaping
library(jsonlite)
library(reshape2)
lst <- fromJSON(json)
lst <- lapply(lst[[1]], unlist)
df <- as.data.frame(lst)
df$key <- rownames(df)
df <- melt(df, id = "key")
df <- dcast(df, formula = variable ~ key)
df
# variable key1 key2 key3 key4 key5 key6
# 1 object_one value1 value2 0 value3 False False
# 2 object_two 0.5 0 343 value4 True True