R/concatenation.R

In altair: Interface to 'Altair'

#' Altair plot concatenation
#'
#' Altair plots can be concatenated using the following operators:
#' `+`, `|`, and `&`
#' @md
#'
#' @param e1 Altair chart object
#' @param e2 Altair chart object
#'
#' @return Compound Altair chart object
#'
#' @rdname altair_concatenation
#' @name altair_concatenation
#' @examples
#'
#' if (interactive()){
#'
#'   # Examples using the beaver1 and beaver2 body temperature data sets
#'   # Layering Charts
#'   base <- alt$Chart(beaver1)$encode(
#'     x = alt$X('time'),
#'     y = alt$Y('temp', scale = alt$Scale(zero = FALSE))
#'   )
#'
#'   scatter_plot <- base$mark_point()
#'   line_plot <- base$mark_line()
#'
#'   combined_plot <- scatter_plot + line_plot
#'
#'   # Horizontal Concatenation
#'   base2 <- alt$Chart(beaver2)$
#'     encode(
#'       x = alt$X("time"),
#'       y = alt$Y("temp", scale = alt$Scale(zero = FALSE))
#'     )
#'
#'   scatter_plot2 <- base2$mark_point()
#'   line_plot2 <- base2$mark_line()
#'
#'   combined_plot <-
#'     (scatter_plot + line_plot)$
#'     properties(title = "Beaver 1", width = 200)
#'
#'   combined_plot2 <-
#'     (scatter_plot2 + line_plot2)$
#'     properties(title = "Beaver 2", width = 200)
#'
#'   hconcat_plot <- combined_plot | combined_plot2
#'
#'   # Vertical Concatenation
#'   vconcat_plot <- combined_plot & combined_plot2
#'
#' }
#'
NULL

is_altair_chart <- function(x) {
  inherits(x, "altair.vegalite.v4.api.TopLevelMixin")
}

#' @rdname altair_concatenation
#' @export
#'
"|.altair.vegalite.v4.api.TopLevelMixin" <- function(e1, e2) {
  if (!is_altair_chart(e2)) {
    stop("Second argument to | is not an Altair Chart")
  }
  alt$hconcat(e1, e2)
}

#' @rdname altair_concatenation
#' @export
#'
"+.altair.vegalite.v4.api.TopLevelMixin" <- function(e1, e2) {
  if (!is_altair_chart(e2)) {
    stop("Second argument to + is not an Altair Chart")
  }
  alt$layer(e1, e2)
}

#' @rdname altair_concatenation
#' @export
#'
"&.altair.vegalite.v4.api.TopLevelMixin" <- function(e1, e2) {
  if (!is_altair_chart(e2)) {
    stop("Second argument to & is not an Altair Chart")
  }
  alt$vconcat(e1, e2)
}