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#' Read a link-node structured JSON file into R as two data frames.
#'
#' \code{JSONtoDF} reads a JSON data file into R and converts part of it to a
#' data frame.
#'
#' @param jsonStr a JSON object to convert. Note if \code{jsonStr} is specified,
#' then \code{file} must be \code{NULL}.
#' @param file character string of the JSON file name. Note if \code{file} is
#' specified, then \code{jsonStr} must be \code{NULL}.
#' @param array character string specifying the name of the JSON array to
#' extract. (JSON arrays are delimited by square brackets).
#'
#' @details \code{JSONtoDF} is intended to load JSON files into R and convert
#' them to data frames that can be used to create network graphs. The command
#' converts the files into R lists and then extracts the JSON array the user
#' would like to make into a data frame.
#'
#' @source Part of the idea for the command comes from mropa's comment on
#' StackExchange:
#' \url{http://stackoverflow.com/questions/4227223/r-list-to-data-frame}.
#'
#' @importFrom rjson fromJSON
#' @importFrom plyr ldply
#' @export
JSONtoDF <- function(jsonStr = NULL, file = NULL, array){
if (!is.null(jsonStr) & !is.null(file)){
stop("Must specify jsonStr OR file.")
}
if (is.null(file)){
MainList <- fromJSON(json_str = jsonStr)
}
if (is.null(jsonStr)){
MainList <- fromJSON(file = file)
}
ArrayList <- MainList[[array]]
MainDF <- ldply(ArrayList, data.frame)
return(MainDF)
}
#' Internal function from Wei Luo to convert a data frame to a JSON array
#'
#' @param dtf a data frame object.
#' @source Function from:
#' \url{http://theweiluo.wordpress.com/2011/09/30/r-to-json-for-d3-js-and-protovis/}
#' @keywords internal
#' @noRd
toJSONarray <- function(dtf){
clnms <- colnames(dtf)
name.value <- function(i){
quote <- '';
if(class(dtf[, i])!='numeric' && class(dtf[, i])!='integer'){
quote <- '"';
}
paste('"', i, '" : ', quote, dtf[,i], quote, sep='')
}
objs <- apply(sapply(clnms, name.value), 1, function(x){paste(x,
collapse=', ')})
objs <- paste('{', objs, '}')
res <- paste('[', paste(objs, collapse=', '), ']')
return(res)
}
#' Read a text file into a single string
#'
#' @source Code taken directly from Ramnath Vaidyanathan's Slidify
#' \url{https://github.com/ramnathv/slidify}.
#' @param doc path to text document
#' @return string with document contents
#' @keywords internal
#' @noRd
read_file <- function(doc, ...){
paste(readLines(doc, ...), collapse = '\n')
}
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