r/R/Table.R

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# to you under the Apache License, Version 2.0 (the
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#
#   http://www.apache.org/licenses/LICENSE-2.0
#
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#' @include R6.R
#'
#' @title class arrow::Table
#'
#' @usage NULL
#' @format NULL
#' @docType class
#'
#' @section Methods:
#'
#' TODO
#'
#' @rdname arrow__Table
#' @name arrow__Table
`arrow::Table` <- R6Class("arrow::Table", inherit = `arrow::Object`,
  public = list(
    column = function(i) shared_ptr(`arrow::Column`, Table__column(self, i)),

    serialize = function(output_stream, ...) write_table(self, output_stream, ...),

    cast = function(target_schema, safe = TRUE, options = cast_options(safe)) {
      assert_that(inherits(target_schema, "arrow::Schema"))
      assert_that(inherits(options, "arrow::compute::CastOptions"))
      assert_that(identical(self$schema$names, target_schema$names), msg = "incompatible schemas")
      shared_ptr(`arrow::Table`, Table__cast(self, target_schema, options))
    },

    select = function(spec) {
      spec <- enquo(spec)
      if (quo_is_null(spec)) {
        self
      } else {
        all_vars <- Table__column_names(self)
        vars <- vars_select(all_vars, !!spec)
        indices <- match(vars, all_vars)
        shared_ptr(`arrow::Table`, Table__select(self, indices))
      }

    }
  ),

  active = list(
    num_columns = function() Table__num_columns(self),
    num_rows = function() Table__num_rows(self),
    schema = function() shared_ptr(`arrow::Schema`, Table__schema(self)),
    columns = function() map(Table__columns(self), shared_ptr, class = `arrow::Column`)
  )
)

#' Create an arrow::Table from a data frame
#'
#' @param ... arrays, chunked arrays, or R vectors
#' @param schema a schema. The default (`NULL`) infers the schema from the `...`
#'
#' @return an arrow::Table
#'
#' @export
table <- function(..., schema = NULL){
  dots <- list2(...)
  # making sure there are always names
  if (is.null(names(dots))) {
    names(dots) <- rep_len("", length(dots))
  }
  stopifnot(length(dots) > 0)
  shared_ptr(`arrow::Table`, Table__from_dots(dots, schema))
}

#' @export
`as.data.frame.arrow::Table` <- function(x, row.names = NULL, optional = FALSE, use_threads = TRUE, ...){
  Table__to_dataframe(x, use_threads = option_use_threads())
}

#' @export
`dim.arrow::Table` <- function(x) {
  c(x$num_rows, x$num_columns)
}