Make deeply nested JSON from data frame in R - json

Question

I'm looking to take a nice tidy data frame and turn it into a deeply nested JSON using R. So far I haven't been able to find any other resources that directly address this task - most seem to be trying to take it in the other direction (un-nesting a JSON).
Here's a small dummy version of the data frame I'm starting with. Imagine a survey was given to two audiences within a company, one for managers and a separate one for employees. The surveys have different sets of questions with different IDs but many questions overlap and I want to compare the responses between the two groups. The end goal is to make a JSON that matches up section IDs, question IDs, and option IDs/text from two surveys in the correct hierarchy. Some questions have subquestions that require a further level of nesting, which is what I’m having difficulty doing.
library(dplyr)
library(tidyr)
library(jsonlite)
dummyDF <- data_frame(sectionId = c(rep(1,9),rep(2,3)),
questionId = c(rep(1,3),rep(2,6),rep(3,3)),
subquestionId = c(rep(NA,3),rep("2a",3),rep("2b",3),rep(NA,3)),
deptManagerQId = c(rep("m1",3),rep("m2",3),rep("m3",3),rep("m4",3)),
deptEmployeeQId = c(rep("e1",3),rep("e3",3),rep("e4",3),rep("e7",3)),
optionId = rep(c(1,2,3),4),
text = rep(c("yes","neutral","no"),4))
And here’s the end result I’m trying to achieve:
theGoal <- fromJSON('{
"sections": [
{
"sectionId": "1",
"questions": [
{
"questionId": "1",
"deptManagerQId": "m1",
"deptEmployeeQId": "e1",
"options": [
{
"optionId": 1,
"text": "yes"
},
{
"optionId": 2,
"text": "neutral"
},
{
"optionId": 3,
"text": "no"
}
]
},
{
"questionId": "2",
"options": [
{
"optionId": 1,
"text": "yes"
},
{
"optionId": 2,
"text": "neutral"
},
{
"optionId": 3,
"text": "no"
}
],
"subquestions": [
{
"subquestionId": "2a",
"deptManagerQId": "m2",
"deptEmployeeQId": "e3"
},
{
"subquestionId": "2b",
"deptManagerQId": "m3",
"deptEmployeeQId": "e4"
}
]
},
{
"questionId": "3",
"deptManagerQId": "m4",
"deptEmployeeQId": "e7",
"options": [
{
"optionId": 1,
"text": "yes"
},
{
"optionId": 2,
"text": "neutral"
},
{
"optionId": 3,
"text": "no"
}
]
}
]
}
]
}')
Here are a few approaches I’ve tried using nest from tidyr that end up either only getting me part of the way there or throwing an error message.
1
list1 <- dummyDF %>% nest(-sectionId, .key=questions) %>%
mutate(questions = lapply(seq_along(.$questions), function(x) nest(.$questions[[x]], optionId, text, .key = options))) %>%
list(sections = .)
2
nested1 <- dummyDF %>% nest(-sectionId, .key=questions) %>%
mutate(questions = lapply(seq_along(.$questions), function(x) nest(.$questions[[x]], optionId, text, .key = options)))
nested2 <- nested1 %>% mutate(questions = lapply(seq_along(.$questions), function(x) nest(.$questions[[x]], subquestionId, .key = subquestions)))
#Gives this error: cannot group column options, of class 'list'
3
list2 <- dummyDF %>% nest(-sectionId, .key=questions) %>%
mutate(questions = lapply(seq_along(.$questions),
function(x) {ifelse(is.na(.$questions[[x]]$subquestionId),
function(x) {.$questions[[x]] %>% select(-subquestionId) %>% nest(optionId, text, .key = options)},
function(x) {.$questions[[x]] %>% nest(subquestion_id, .key = subquestions)})})) %>%
list(sections = .)
#Gives this error: attempt to replicate an object of type 'closure'
Any ideas would be greatly appreciated. I’m open to any approaches. I took the issue to a local R user group meet-up but wasn’t able to come up with any solutions so I’ve got my fingers crossed here. I realize R might not be the best tool to accomplish this but it’s the one I know so I’m giving it a shot. Thanks.

Answer 1

jsonlite::toJSON looks like a nice solution to your problem.
Works seamlessly up to column types and column order (I corrected to illustrate that the objects were identical). If you need any other type of JSON structure, I would recommend restructuring the data_frame on the front end first using something like dplyr or tidyr.
library(jsonlite)
library(dplyr)
dummyDF <- data_frame(sectionId = c(rep(1,9),rep(2,3)),
questionId = c(rep(1,3),rep(2,6),rep(3,3)),
subquestionId = c(rep(NA,3),rep("2a",3),rep("2b",3),rep(NA,3)),
deptManagerQId = c(rep("m1",3),rep("m2",3),rep("m3",3),rep("m4",3)),
deptEmployeeQId = c(rep("e1",3),rep("e3",3),rep("e4",3),rep("e7",3)),
optionId = rep(c(1,2,3),4),
text = rep(c("yes","neutral","no"),4))
## Convert to a JSON object
json <- jsonlite::toJSON(dummyDF)
theGoal <- fromJSON(json) %>% tbl_df() %>% select_(.dots=names(dummyDF)) %>%
## Convert integer columns to numeric
mutate_if(function(x) {if (typeof(x)=='integer') {TRUE} else {FALSE}},as.numeric)
## Compare the objects
all.equal(theGoal,dummyDF)
# TRUE
identical(theGoal,dummyDF)
# TRUE