JSON with jsonlite in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to convert a list to JSON using jsonlite.

R Programming

library(jsonlite)
my_list <- list(name = "Alice", age = 25)
json_data <- toJSON([1])
print(json_data)

Drag options to blanks, or click blank then click option'

Ajson_data

Bmy_list

Clist

DtoJSON

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the result variable instead of the data variable.

Using the function name inside itself.

The toJSON() function converts an R object like my_list into JSON format.

2fill in blank

medium

Complete the code to prettify JSON output with jsonlite.

R Programming

library(jsonlite)
my_list <- list(city = "Paris", population = 2148327)
json_data <- toJSON(my_list, [1] = TRUE)
cat(json_data)

Drag options to blanks, or click blank then click option'

Aauto_unbox

Bdigits

CsimplifyVector

Dpretty

Attempts:

3 left

💡 Hint

Common Mistakes

Using auto_unbox which controls single values, not formatting.

Confusing digits with formatting.

The pretty = TRUE option formats JSON with indentation and line breaks for readability.

3fill in blank

hard

Fix the error in the code to parse JSON string back to R object.

R Programming

library(jsonlite)
json_str <- '{"fruit":"apple","count":10}'
my_data <- [1](json_str)
print(my_data)

Drag options to blanks, or click blank then click option'

AfromJSON

BparseJSON

CtoJSON

Djsonlite

Attempts:

3 left

💡 Hint

Common Mistakes

Using toJSON() which converts R to JSON, not the other way.

Using a non-existent function parseJSON().

The fromJSON() function converts a JSON string back into an R object.

4fill in blank

hard

Fill both blanks to create a JSON from a named vector and parse it back.

R Programming

library(jsonlite)
vec <- c(a = 1, b = 2, c = 3)
json_vec <- [1](vec, [2] = TRUE)
parsed_vec <- fromJSON(json_vec)
print(parsed_vec)

Drag options to blanks, or click blank then click option'

AtoJSON

Bpretty

Cauto_unbox

DfromJSON

Attempts:

3 left

💡 Hint

Common Mistakes

Using fromJSON in the first blank which is for parsing JSON.

Using auto_unbox instead of pretty for formatting.

Use toJSON() to convert the vector, and pretty = TRUE to format the JSON nicely.

5fill in blank

hard

Fill all three blanks to convert a data frame to JSON with unboxed values and parse it back.

R Programming

library(jsonlite)
df <- data.frame(name = c("Tom", "Sue"), age = c(30, 25))
json_df <- [1](df, [2] = TRUE)
parsed_df <- [3](json_df)
print(parsed_df)

Drag options to blanks, or click blank then click option'

AtoJSON

Bauto_unbox

CfromJSON

Dpretty

Attempts:

3 left

💡 Hint

Common Mistakes

Using pretty instead of auto_unbox for the second blank.

Using toJSON instead of fromJSON for parsing.

Use toJSON() to convert the data frame, auto_unbox = TRUE to avoid arrays for single values, and fromJSON() to parse back.

Practice

1. What is the main purpose of the jsonlite package in R?

easy

A. To manage databases

B. To create graphical plots

C. To perform statistical tests

D. To convert R objects to JSON format and back

Solution

1. Step 1: Understand jsonlite's functionality

   The jsonlite package is designed to handle JSON data in R, allowing conversion between R objects and JSON text.

2. Step 2: Identify the correct purpose

   Among the options, only converting R objects to JSON and back matches jsonlite's main use.

3. Final Answer:

   To convert R objects to JSON format and back -> Option D

4. Quick Check:

   jsonlite = convert R and JSON [OK]

Hint: jsonlite = R to JSON and back conversion [OK]

Common Mistakes:

• Confusing jsonlite with plotting packages
• Thinking jsonlite manages databases
• Assuming jsonlite performs statistical tests

2. Which of the following is the correct syntax to convert an R list my_list to JSON text using jsonlite?

easy

A. jsonlite::toJSON(my_list)

B. jsonlite::fromJSON(my_list)

C. toJSON(my_list, jsonlite)

D. fromJSON(my_list, jsonlite)

Solution

1. Step 1: Identify the function to convert R to JSON

   The function to convert R objects to JSON in jsonlite is toJSON().

2. Step 2: Check correct usage with namespace

   Using jsonlite::toJSON(my_list) correctly calls the function from the package.

3. Final Answer:

   jsonlite::toJSON(my_list) -> Option A

4. Quick Check:

   toJSON converts R to JSON [OK]

Hint: Use toJSON() to convert R data to JSON [OK]

Common Mistakes:

• Using fromJSON() to convert R to JSON
• Passing package name as argument
• Mixing function names and arguments

3. What will be the output of the following R code?

library(jsonlite)
my_list <- list(name = "Anna", age = 25)
json_text <- toJSON(my_list, auto_unbox = TRUE)
cat(json_text)

medium

A. {"name":"Anna","age":25}

B. ["Anna",25]

C. {"name":["Anna"],"age":[25]}

D. Error: object 'toJSON' not found

Solution

1. Step 1: Understand toJSON with auto_unbox

   The toJSON() function converts the list to JSON. The auto_unbox=TRUE option removes array brackets for single values.

2. Step 2: Analyze the output format

   The list has named elements "name" and "age" with single values, so JSON will be an object with those keys and unboxed values.

3. Final Answer:

   {"name":"Anna","age":25} -> Option A

4. Quick Check:

   toJSON with auto_unbox = unboxed JSON object [OK]

Hint: auto_unbox=TRUE removes brackets for single values [OK]

Common Mistakes:

• Ignoring auto_unbox and expecting arrays
• Confusing JSON arrays with objects
• Forgetting to load jsonlite package

4. Identify the error in this R code snippet using jsonlite:

library(jsonlite)
json_text <- '{"x":10, "y":20}'
my_data <- toJSON(json_text)

medium

A. Variable my_data is not assigned correctly

B. Missing library(jsonlite) call

C. toJSON() is used instead of fromJSON() to parse JSON text

D. JSON text is not properly formatted

Solution

1. Step 1: Check function usage for JSON parsing

   The code tries to convert JSON text to R data. The correct function for this is fromJSON(), not toJSON().

2. Step 2: Confirm other parts are correct

   The JSON text is valid, and the library is loaded, so the main error is the wrong function call.

3. Final Answer:

   toJSON() is used instead of fromJSON() to parse JSON text -> Option C

4. Quick Check:

   Use fromJSON() to read JSON text [OK]

Hint: Use fromJSON() to read JSON text, not toJSON() [OK]

Common Mistakes:

• Using toJSON() to read JSON text
• Not loading jsonlite package
• Incorrect JSON string format

5. You have a JSON string representing a list of users:

json_users <- '[{"name":"John","age":30},{"name":"Jane","age":25}]'

How can you convert this JSON into an R data frame with columns name and age using jsonlite?

hard

A. df <- toJSON(json_users)

B. df <- fromJSON(json_users)

C. df <- as.data.frame(toJSON(json_users))

D. df <- as.list(fromJSON(json_users))

Solution

1. Step 1: Identify function to parse JSON to R

   The fromJSON() function converts JSON text into R objects, including data frames when JSON is an array of objects.

2. Step 2: Confirm output type matches requirement

   Since the JSON is a list of user objects, fromJSON() returns a data frame with columns for each key.

3. Final Answer:

   df <- fromJSON(json_users) -> Option B

4. Quick Check:

   fromJSON() parses JSON array to data frame [OK]

Hint: Use fromJSON() to convert JSON array to data frame [OK]

Common Mistakes:

• Using toJSON() instead of fromJSON()
• Converting JSON to list instead of data frame
• Trying to convert JSON string directly with as.data.frame()