Reading Local JSON Files in R

The following example is a way of reading local JSON files into R scripts. This can be useful for config files, although it's still also acceptable for data files as well.

Import package to work with JSON and lists

require(rlist)
require(rjson)

Load file into script

configPath <- '.'
fileName <- 'config.json'
jsonFile <- fromJSON(file=paste(configPath,fileName,sep="/"),method="C")

The data gets loaded in as a list. It may be tedious to access nested contents via indices. To aid with this, a helper function can be created to extract the individual nested data elements of the file.

#Extract values form nested list
#top_level = list.select(obj$topkey,obj$subkey)
extractData <- function(top_level) {
    output <- unlist(lapply(top_level,'[[',1));
    return(output);
}

Extract data

Below is a default sample json file that includes both nested and non-nested data.

{
    "port": 2100,
    "connectionStrings": {
        "default": "123.567.890"
    }
}

The data in that file can be accessed as shown below.

#Not Nested
port <- config$port # Should store 2100

#Nested
connectionString <- extractData(list.select(config$connectionStrings,default)) #Should store 123.567.890

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