R/infer.R

In frictionlessdata/tableschema-r: Table Schema 'Frictionless Data'

#' Infer source schema
#' @description Given data source and headers infer will return a Table Schema based on the data values.
#' @param source data source, one of:
#' \itemize{
#'  \item string with the local CSV file (path)
#'  \item string with the remote CSV file (url)
#'  \item list of lists representing the rows
#'  \item readable stream with CSV file contents
#'  \item function returning readable stream with CSV file contents
#'  }
#' @param options any \code{\link{Table.load}} options
#' @rdname infer
#' @export
#' @return Schema descriptor
#' @examples
#' # list of lists data source
#' source = list(
#'              list("id"= 1,
#'                   "age"= 39,
#'                   "name"= "Paul"),
#'              list("id"= 2,
#'                   "age"= 23,
#'                   "name"= "Jimmy"),
#'              list("id"= 3,
#'                   "age"= 36,
#'                   "name"= "Jane"),
#'              list("id"= 4,
#'                   "age"= 28,
#'                   "name"= "Judy"))
#' 
#' infer(source, options=list(headers=list("id","age","name")))$fields
#' 

# Module API

infer <- function(source, options = list()) {
  
  # https://github.com/frictionlessdata/tableschema-js#infer
  arguments <- list(source)
  arguments <- append(arguments, options)

  def2 <- do.call(Table.load, arguments )
  table <- future::value(def2)
  

  descriptor <- table$infer(limit = options[["limit"]])
  
  return(descriptor)
}