R/list.parse.R

In rlist: A Toolbox for Non-Tabular Data Manipulation

#' Convert an object to list with identical structure
#'
#' This function converts an object representing data to
#' list that represents the same data. For example, a
#' \code{data.frame} stored tabular data column-wisely,
#' that is, each column represents a vector of a certain
#' type. \code{list.parse} converts a \code{data.frame} to
#' a list which represents the data row-wisely so that it
#' can be more convinient to perform other non-tabular data
#' manipulation methods.
#' @param x \code{An object}
#' @param ... Additional parameters passed to converter function
#' @return \code{list} object representing the data in \code{x}
#' @export
#' @examples
#' x <- data.frame(a=1:3,type=c('A','C','B'))
#' list.parse(x)
#'
#' x <- matrix(rnorm(1000),ncol=5)
#' rownames(x) <- paste0('item',1:nrow(x))
#' colnames(x) <- c('a','b','c','d','e')
#' list.parse(x)
#'
#' z <- '
#' a:
#'   type: x
#'   class: A
#'   registered: yes
#' '
#' list.parse(z, type='yaml')
list.parse <- function(x, ...) UseMethod("list.parse")

#' @export
#' @rdname list.parse
list.parse.default <- function(x, ...) {
  as.list(x, ...)
}

#' @export
#' @rdname list.parse
list.parse.matrix <- function(x, ...) {
  apply(x, 1L, as.vector, mode = "list")
}

#' @export
#' @rdname list.parse
list.parse.data.frame <- function(x, ...) {
  cols <- colnames(x)
  items <- map(function(...) setnames(list(...), cols), x)
  setnames(items, rownames(x))
}

#' @export
#' @rdname list.parse
#' @param type The type of data to parse. Currently json and yaml are supported.
list.parse.character <- function(x, type, ...) {
  if (length(x) == 0L)
    return(list()) else if (length(x) == 1L) {
    if (missing(type) || length(type) == 0L || is.na(type)) {
      list.parse.default(x, ...)
    } else if (tolower(type) == "yaml") {
      yaml::yaml.load(x, ...)
    } else if (tolower(type) == "json") {
      callwith(jsonlite::fromJSON, list(x, simplifyVector = FALSE, simplifyDataFrame = FALSE,
        simplifyMatrix = FALSE), list(...))
    } else if (tolower(type) == "xml") {
      XML::xmlToList(XML::xmlParseString(x, ...))
    } else {
      stop("Unsupported type of data", call. = FALSE)
    }
  } else if (length(x) > 1L) {
    map(list.parse.character, list(x, type), list(...), use.names = FALSE)
  }
}