Question

I suspect I’m missing something obvious here, but how do I parse deeply nested structures in R using RJSONIO?

For example – suppose I directly want to reference $familyName in results.data.json$MRData$RaceTable$Races[[1]]$Results[[8]]$Driver as grabbed using the following snippet:

require(RJSONIO)
resultsURL='http://ergast.com/api/f1/2012/1/results.json'
results.data.json=fromJSON(resultsURL)

RJSONIO doesn’t appear to want to parse the ..$Results[[i]] data as structured elements?

Answer 1

require(RJSONIO)

somedata1<-list(a=1,b='w')
fromJSON(toJSON(somedata1))
# $a
# [1] 1

# $b
# [1] "w"

somedata2<-list(a=1,b=2)
fromJSON(toJSON(somedata2))
# a b 
# 1 2 

somedata3<-list(a='v',b='w')
fromJSON(toJSON(somedata3))
#  a   b 
# "v" "w" 

fromJSON(toJSON(somedata3),simplify=StrictNumeric)
# $a
# [1] "v"

# $b
# [1] "w"

fromJSON(toJSON(somedata2),simplify=FALSE)
# $a
# [1] 1

# $b
# [1] 2

fromJSON(toJSON(somedata3),simplifyWithNames = FALSE)
# $a
# [1] "v"

# $b
# [1] "w"


fromJSON(toJSON(somedata2),simplifyWithNames = FALSE)
# $a
# [1] 1

# $b
# [1] 2

from the examples above by default RJSON simplifies “collections/arrays of homogeneous scalar elements to R vectors”. This simplification can be controlled using simplify or simplifyWithNames. In your example you can do any of the following to access the element you want:

require(RJSONIO)
resultsURL='http://ergast.com/api/f1/2012/1/results.json'
results.data.json=fromJSON(resultsURL)
results.data.json$MRData$RaceTable$Races[[1]]$Results[[8]]$Driver['familyName']
# familyName 
#    "Pérez" 

results.data.json=fromJSON(resultsURL,simplify=FALSE)
results.data.json$MRData$RaceTable$Races[[1]]$Results[[8]]$Driver$familyName
# [1] "Pérez"

results.data.json=fromJSON(resultsURL,simplify=StrictNumeric)
results.data.json$MRData$RaceTable$Races[[1]]$Results[[8]]$Driver$familyName
# [1] "Pérez"

results.data.json=fromJSON(resultsURL,simplifyWithNames = FALSE)
results.data.json$MRData$RaceTable$Races[[1]]$Results[[8]]$Driver$familyName
# [1] "Pérez"