R/tribble.R

In Robertus100/tibble: Simple Data Frames

#' Row-wise tibble creation
#'
#' Create [tibble]s using an easier to read row-by-row layout.
#' This is useful for small tables of data where readability is
#' important.  Please see \link{tibble-package} for a general introduction.
#'
#' `frame_data()` is an older name for `tribble()`. It will eventually
#' be phased out.
#'
#' @param ... Arguments specifying the structure of a `tibble`.
#'   Variable names should be formulas, and may only appear before the data.
#' @return A [tibble].
#' @export
#' @examples
#' tribble(
#'   ~colA, ~colB,
#'   "a",   1,
#'   "b",   2,
#'   "c",   3
#' )
#'
#' # tribble will create a list column if the value in any cell is
#' # not a scalar
#' tribble(
#'   ~x,  ~y,
#'   "a", 1:3,
#'   "b", 4:6
#' )
tribble <- function(...) {
  data <- extract_frame_data_from_dots(...)
  turn_frame_data_into_tibble(data$frame_names, data$frame_rest)
}

#' @export
#' @rdname tribble
frame_data <- tribble

#' Row-wise matrix creation
#'
#' Create matrices laying out the data in rows, similar to
#' `matrix(..., byrow = TRUE)`, with a nicer-to-read syntax.
#' This is useful for small matrices, e.g. covariance matrices, where readability
#' is important. The syntax is inspired by [tribble()].
#'
#' @param ... Arguments specifying the structure of a `frame_matrix`.
#'   Column names should be formulas, and may only appear before the data.
#' @return A [matrix].
#' @export
#' @examples
#' frame_matrix(
#'   ~col1, ~col2,
#'   1,     3,
#'   5,     2
#' )
frame_matrix <- function(...) {
  data <- extract_frame_data_from_dots(...)
  turn_frame_data_into_frame_matrix(data$frame_names, data$frame_rest)
}

extract_frame_data_from_dots <- function(...) {
  dots <- list(...)

  # Extract the names.
  frame_names <- extract_frame_names_from_dots(dots)

  # Extract the data
  if (length(frame_names) == 0 && length(dots) != 0) {
    stopc("expected at least one column name; e.g. '~name'")
  }
  frame_rest <- dots[-seq_along(frame_names)]
  if (length(frame_rest) == 0L) {
    # Can't decide on type in absence of data -- use logical which is
    # coercible to all types
    frame_rest <- logical()
  }

  validate_rectangular_shape(frame_names, frame_rest)

  list(frame_names = frame_names, frame_rest = frame_rest)
}

extract_frame_names_from_dots <- function(dots) {
  frame_names <- character()

  for (i in seq_along(dots)) {
    el <- dots[[i]]
    if (!is.call(el))
      break

    if (!identical(el[[1]], as.name("~")))
      break

    if (length(el) != 2) {
      stopc("expected a column name with a single argument; e.g. '~name'")
    }

    candidate <- el[[2]]
    if (!(is.symbol(candidate) || is.character(candidate))) {
      stopc("expected a symbol or string denoting a column name")
    }

    frame_names <- c(frame_names, as.character(el[[2]]))
  }

  frame_names
}

validate_rectangular_shape <- function(frame_names, frame_rest) {
  if (length(frame_names) == 0 && length(frame_rest) == 0) return();

  # Figure out the associated number of rows and number of columns,
  # and validate that the supplied formula produces a rectangular
  # structure.
  if (length(frame_rest) %% length(frame_names) != 0) {
    stopc(
      sprintf(
        "invalid specification: had %s elements and %s columns",
        length(frame_rest),
        length(frame_names)
      )
    )
  }
}

turn_frame_data_into_tibble <- function(names, rest) {
  frame_mat <- matrix(rest, ncol = length(names), byrow = TRUE)
  frame_col <- turn_matrix_into_column_list(frame_mat)

  # Create a tbl_df and return it
  names(frame_col) <- names
  as_tibble(frame_col)
}

turn_matrix_into_column_list <- function(frame_mat) {
  frame_col <- vector("list", length = ncol(frame_mat))
  # if a frame_mat's col is a list column, keep it unchanged (does not unlist)
  for (i in seq_len(ncol(frame_mat))) {
    col <- frame_mat[, i]
    if (any(vapply(col, needs_list_col, logical(1L)))) {
      frame_col[[i]] <- col
    } else {
      frame_col[[i]] <- unlist(col)
    }
  }
  return(frame_col)
}

turn_frame_data_into_frame_matrix <- function(names, rest) {
  if (any(vapply(rest, needs_list_col, logical(1)))) {
    stopc("frame_matrix() cannot have list columns")
  }

  frame_ncol <- length(names)
  frame_mat <- matrix(unlist(rest), ncol = frame_ncol, byrow = TRUE)

  colnames(frame_mat) <- names
  frame_mat
}