Converting datatable to a set of JSON objects in R

Question

I want to convert a data table in R to a set of json objects: Suppose my datatable looks like this:

name           group    age (y) height (cm) weight (kg) score
[1,] "Doe, John"    "Red"    "24"    "182"       "74.8"      NA   
[2,] "Doe, Jane"    "Green"  "30"    "170"       "70.1"      "500"
[3,] "Smith, Joan"  "Yellow" "41"    "169"       "60"        NA   
[4,] "Brown, Sam"   "Green"  "22"    "183"       "75"        "865"
[5,] "Jones, Larry" "Green"  "31"    "178"       "83.9"      "221"
[6,] "Murray, Seth" "Red"    "35"    "172"       "76.2"      "413"
[7,] "Doe, Jane"    "Yellow" "22"    "164"       "68"        "902"

I want it as follows:

[{"name":"Doe, John","group":"Red","age (y)":24,"height (cm)":182,"weight (kg)":74.8,"score":null},
{"name":"Doe, Jane","group":"Green","age (y)":30,"height (cm)":170,"weight (kg)":70.1,"score":500},
{"name":"Smith, Joan","group":"Yellow","age (y)":41,"height (cm)":169,"weight (kg)":60,"score":null},
{"name":"Brown, Sam","group":"Green","age (y)":22,"height (cm)":183,"weight (kg)":75,"score":865},
{"name":"Jones, Larry","group":"Green","age (y)":31,"height (cm)":178,"weight (kg)":83.9,"score":221},
{"name":"Murray, Seth","group":"Red","age (y)":35,"height (cm)":172,"weight (kg)":76.2,"score":413},
{"name":"Doe, Jane","group":"Yellow","age (y)":22,"height (cm)":164,"weight (kg)":68,"score":902}]

Can anybody help me with this?

MrFlick · Accepted Answer · 2014-09-12 06:03:53Z

1

Are you sure that's data.table output? The [1,] looks funny to me. I thought data.table usually did 1:. That looks more like matrix output.

But assuming it is a data.table like

dd<-data.table(
    name = c("Doe, John", "Doe, Jane", "Smith, Joan", "Brown, Sam",
        "Jones, Larry", "Murray, Seth", "Doe, Jane"), 
    group = c("Red", "Green", "Yellow", "Green", "Green", "Red", "Yellow"), 
    "age (y)" = c(24L, 30L, 41L, 22L, 31L, 35L, 22L),
    "height (cm)" = c(182L, 170L, 169L, 183L, 178L, 172L, 164L), 
    "weight (kg)" = c(74.8, 70.1, 60, 75, 83.9, 76.2, 68), 
    score = c(NA, 500L, NA, 865L, 221L, 413L, 902L)
)

then you can run

cat( toJSON( unname(split(dd, 1:nrow(dd))) ) )

to get your desired output.

answered Sep 12, 2014 at 6:03

MrFlick

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3 Comments

Rabiya Ashruff Over a year ago

Sorry my bad. You are right!! I posted a dataframe I guess.Your answer works!! Thanks a ton!!! :)

Rabiya Ashruff Over a year ago

Hey I see that the values in json objects are enclosed in square brackets like this: "name": [ "Doe, Jane" ] Is it possible to get them without the square brackets?

MrFlick Over a year ago

@RabiyaAshruff That doesn't happen for me when i run the code above (using R version 3.1.0 and rjson_0.2.14 and data.table_1.9.2). I get output that looks like what you desire. Can you make a reproducible example?

David Arenburg · Accepted Answer · 2014-09-12 08:17:29Z

0

You can try tp use fromJSON or toJSON on the jsonlite package.

library(jsonlite)

iris2 <- fromJSON(myjson)

myjson <- toJSON(iris, pretty=TRUE)

hope it helps.

edited Sep 12, 2014 at 8:17

David Arenburg

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answered Sep 12, 2014 at 6:10

jubert roldan

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1 Comment

Rabiya Ashruff Over a year ago

Hi I had actually tried that before. But it doesn't give the desired output. It just produces a single json object with all values separated by comma with no field names.

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