Enable Operation on Lists of Plots

[billdenney]

As described in #93, I often operate on many plots that have similar features. I would love it if there were the ability to work with a list of plots as though they were a single plot. I could imagine that this would dovetail in with the request in #7 to print all pages in facet_wrap_paginate() or facet_grid_paginate(). What I'm thinking of would look something like the following, but I can't find a way to make it work with a simple + instead of %+list%:

library(ggplot2)
library(ggforce)

as_gg_list <- function(x) {
  UseMethod("as_gg_list")
}

as_gg_list.gg <- function(x) {
  if (is.null(n_pages(x))) {
    as_gg_list(list(x))
  } else {
    ret <- list()
    for (idx in seq_len(n_pages(x))) {
      new_facet <-
        ggproto(
          NULL, FacetWrapPaginate,
          shrink = x$facet$shrink,
          params = c(
            x$facet$params[setdiff(names(x$facet$params), "page")],
            list(page = idx)
          )
        )
      ret[[idx]] <- x + new_facet
    }
    as_gg_list(ret)
  }
}

as_gg_list.list <- function(x) {
  class(x) <- "gg_list"
  x
}

print.gg_list <- function(x, ..., fig_suffix = "\n\n") {
  for (idx in seq_along(x)) {
    print(x[[idx]])
    cat(fig_suffix)
  }
}

`%+list%` <- function(e1, e2) {
  as_gg_list(
    lapply(X=e1, FUN="+", e2)
  )
}

p <-
  ggplot(diamonds, aes(x=carat, y=price)) +
  geom_hex() +
  facet_wrap_paginate(facets="color", nrow=1, ncol=1)

n_pages(p)

p_list <- as_gg_list(p)
p_list_2 <- p_list %+list% scale_y_log10()

p_list_2 <- p_list + scale_y_log10()

[billdenney]

I kept bashing my head against it a bit longer, and I came up with an implementation that will work if you use %+% instead of +. If I improved the documentation, do you think this would be a good fit for ggforce? (If so, I'll add documentation and make it into a PR.)

library(ggplot2)
library(ggforce)

as_gg_list <- function(x) {
  UseMethod("as_gg_list")
}

as_gg_list.gg <- function(x) {
  if (is.null(n_pages(x))) {
    as_gg_list(list(x))
  } else {
    ret <- list()
    for (idx in seq_len(n_pages(x))) {
      new_facet <-
        ggproto(
          NULL, FacetWrapPaginate,
          shrink = x$facet$shrink,
          params = c(
            x$facet$params[setdiff(names(x$facet$params), "page")],
            list(page = idx)
          )
        )
      ret[[idx]] <- x + new_facet
    }
    as_gg_list(ret)
  }
}

as_gg_list.list <- function(x) {
  class(x) <- c("gg_list", "gg")
  x
}

print.gg_list <- function(x, ..., fig_suffix = "\n\n") {
  for (idx in seq_along(x)) {
    print(x[[idx]])
    cat(fig_suffix)
  }
}

`%+%` <- function(e1, e2) {
  UseMethod("%+%")
}

`%+%.gg_list` <- function(e1, e2) {
  as_gg_list(
    lapply(X=e1, FUN="+", e2)
  )
}

`%+%.default` <- function(e1, e2) {
  ggplot2::`%+%`(e1, e2)
}

ggplot.list <- function(data=NULL, mapping = aes(), ..., environment = parent.frame()) {
  as_gg_list(
    lapply(
      X=data,
      FUN=ggplot,
      mapping=mapping,
      ...,
      environment=environment
    )
  )
}

d_list <- split(diamonds, f=diamonds$color)
p <-
  ggplot(diamonds, aes(x=carat, y=price)) +
  geom_hex() +
  facet_wrap_paginate(facets="color", nrow=1, ncol=1)

n_pages(p)

p_list <- as_gg_list(p)
p_list_2 <- p_list %+% scale_y_log10()

p_list_3 <-
  ggplot(d_list, aes(x=carat, y=price)) %+%
  geom_hex() %+%
  facet_wrap(~color)

[thomasp85]

I don't think this is a good fit for ggforce, as the focus is to provide new geoms/stats/facets etc, not add a new operator

[billdenney]

In case someone else has this use case, I'm about to release the ggtibble package on CRAN: https://github.com/billdenney/ggtibble

(I agree that it's not a good fit for ggforce-- but knowing of this other package may help others who may find this issue and have the same goal.)