R/fortify.R

In ggplot2: Create Elegant Data Visualisations Using the Grammar of Graphics

#' Fortify a model with data.
#'
#' Rather than using this function, I now recommend using the \pkg{broom}
#' package, which implements a much wider range of methods. `fortify()`
#' may be deprecated in the future.
#'
#' @family plotting automation topics
#' @seealso [fortify.lm()]
#' @param model model or other R object to convert to data frame
#' @param data original dataset, if needed
#' @param ... other arguments passed to methods
#' @export
fortify <- function(model, data, ...) UseMethod("fortify")

#' @export
fortify.data.frame <- function(model, data, ...) model
#' @export
fortify.tbl_df <- function(model, data, ...) model
#' @export
fortify.tbl <- function(model, data, ...) {
  check_installed("dplyr", reason = "to work with `tbl` objects.")
  dplyr::collect(model)
}
#' @export
fortify.NULL <- function(model, data, ...) waiver()
#' @export
fortify.function <- function(model, data, ...) model
# accept purrr-style lambda notation
#' @export
fortify.formula <- function(model, data, ...) as_function(model)
#' @export
fortify.grouped_df <- function(model, data, ...) {
  check_installed("dplyr", reason = "to work with `grouped_df` objects.")
  model$.group <- dplyr::group_indices(model)
  model
}

# We rely on object behavior rather than type to determine whether 'data' is
# an acceptable data-frame-like object or not. For this, we check that dim(),
# colnames(), and as.data.frame() behave in a healthy manner on 'data',
# and that their behaviors are aligned (i.e. that as.data.frame() preserves
# the original dimensions and colnames). Note that we don't care about what
# happens to the rownames.
# There are a lot of ways that dim(), colnames(), or as.data.frame() could
# do non-sensical things (they are not even guaranteed to work!) hence the
# paranoid mode.
.prevalidate_data_frame_like_object <- function(data) {
  orig_dims <- dim(data)
  if (!vec_is(orig_dims, integer(), size=2))
    cli::cli_abort(paste0("{.code dim(data)} must return ",
                          "an {.cls integer} of length 2."))
  if (anyNA(orig_dims) || any(orig_dims < 0))  # extra-paranoid mode
    cli::cli_abort(paste0("{.code dim(data)} can't have {.code NA}s ",
                          "or negative values."))
  orig_colnames <- colnames(data)
  if (!vec_is(orig_colnames, character(), size = ncol(data)))
    cli::cli_abort(paste0("{.code colnames(data)} must return a ",
                          "{.cls character} of length {.code ncol(data)}."))
}
.postvalidate_data_frame_like_object <- function(df, data) {
  msg0 <- "{.code as.data.frame(data)} must "
  if (!is.data.frame(df))
    cli::cli_abort(paste0(msg0, "return a {.cls data.frame}."))
  if (!identical(dim(df), dim(data)))
    cli::cli_abort(paste0(msg0, "preserve dimensions."))
  if (!identical(colnames(df), colnames(data)))
    cli::cli_abort(paste0(msg0, "preserve column names."))
}
validate_as_data_frame <- function(data) {
  if (is.data.frame(data))
    return(data)
  .prevalidate_data_frame_like_object(data)
  df <- as.data.frame(data)
  .postvalidate_data_frame_like_object(df, data)
  df
}

#' @export
fortify.default <- function(model, data, ...) {
  msg0 <- paste0(
    "{{.arg data}} must be a {{.cls data.frame}}, ",
    "or an object coercible by {{.fn fortify}}, or a valid ",
    "{{.cls data.frame}}-like object coercible by {{.fn as.data.frame}}"
  )
  if (inherits(model, "uneval")) {
    msg <- c(
      glue(msg0, ", not {obj_type_friendly(model)}."),
      "i" = "Did you accidentally pass {.fn aes} to the {.arg data} argument?"
    )
    cli::cli_abort(msg)
  }
  msg0 <- paste0(msg0, ". ")
  try_fetch(
    validate_as_data_frame(model),
    error = function(cnd) cli::cli_abort(glue(msg0), parent = cnd)
  )
}