rggplot2facetclipping

control per-axis ggplot2 clipping


This is an extension beyond a previous question, where the goal was to set different limits for each facet. The code from that question is stored in a gist, and has been in production since.

A quick demo with sample data:

set.seed(42)
dat <- data.frame(x = seq(0,1,len=101), y = cumsum(runif(101,-1,1)), z=sample(1:3, size=101, replace=TRUE))
dat$y <- dat$y * dat$z
dat$y[50] <- 99
dat$z[50] <- 2L
lims <- data.frame(z=1:3, ymin=0, ymax=c(10,25,30))

ggplot(dat, aes(x, y)) +
  facet_grid(z ~ ., switch="both", scales="free_y") +
  scale_x_continuous(expand = c(0, 0)) +
  geom_line() +
  coord_cartesian_panels(panel_limits = lims, clip = "on")

ggplot2 with per-facet limits

I now have a need to add geom_labels to the right side of the plot, outside of plot region. Edit: multiple labels per facet, with colors (whose order is inconsistent between facets). Doing this is relatively straight-forward: place the label at the edge of the screen, extend the theme's plot.margin, and turn off clipping. Unfortunately, as you might imagine with the two excursions in facets 2 and 3, disabling clipping is a concern.

summ <- aggregate(y ~ z, dat, FUN = function(z) c(lo=mean(z)-3, hi=mean(z)+3)) |>
  do.call(data.frame, args = _) |>
  reshape2::melt("z", variable.name = "ign", value.name = "y") |>
  transform(lbl = sprintf("%0.03f", y)) |>
  transform(fill = factor(ave(z, z, FUN = function(ign) sample(seq_along(ign)))))

ggplot(dat, aes(x, y)) +
  facet_grid(z ~ ., switch="both", scales="free_y") +
  scale_x_continuous(expand = c(0, 0)) +
  geom_line() +
  geom_label(x = 1, aes(y = y, label = lbl, fill = fill), data = summ, hjust = -0.1) +
  coord_cartesian_panels(panel_limits = lims, clip = "off") +
  theme(plot.margin = unit(c(0.5, 0.65 * max(nchar(summ$lbl)), 0.5, 0.5), "char")) +
  scale_fill_discrete(guide = "none")

ggplot2 with side labels and broken clipping

I supposed there are three possible ways to resolve this:

  1. Find another way to add the labels on the right side that does not require disabling clipping. To be clear, theming (background, axis lines/ticks/labels, etc) should not be affected by this. There are many other components to these plots here, I need the plot region to "stop" cleanly before the labels begin.

  2. Find a way to clip on the y axis and not the x. In this case I have "strict" control over the x-values so am not as concerned about running amuck on either the left or right side.

  3. Incorporate oob use (e.g., scales::oob_squish) into the ggproto use within coord_cartesian_panels.

  4. Something else?


Solution

  • (I suppose there are reasons not to consider plotting the labels separately & combining the results together using one of the usual suspects such as cowplot, patchwork, etc.)

    I wrote a modified version of FacetGrid that could accept separate clipping instructions for each layer. Combine that with specifying clip = c("on", "off") in coord_cartesian_panels seems to work.

    Note: having a legend positioned to the right of the plot (i.e. default legend position) will mess up the appearance, but I'd consider that an intrinsic part of the way ggplot grobs are laid out. Since the use case here doesn't place a legend on the right, I assume it's not a key requirement for now.

    Demonstration with same use case in the question:

    ggplot(dat, aes(x, y)) +
      facet_grid2(z ~ ., switch="both", scales="free_y") +
      scale_x_continuous(expand = c(0, 0)) +
      geom_line() +
      geom_label(x = 1, aes(y = y, label = lbl, fill = fill), data = summ, hjust = -0.1) +
      coord_cartesian_panels(panel_limits = lims, clip = c("on", "off")) +
      theme(plot.margin = unit(c(0.5, 0.65 * max(nchar(summ$lbl)), 0.5, 0.5), "char")) +
      scale_fill_discrete(guide = "none")
    

    result

    Further demonstration for layer-specific clipping by adding another geom layer, but this one clipped at the edge:

    ggplot(dat, aes(x, y)) +
      facet_grid2(z ~ ., switch="both", scales="free_y") +
      scale_x_continuous(expand = c(0, 0)) +
      geom_line() +
      geom_label(x = 1, aes(y = y, label = lbl, fill = fill), data = summ, hjust = -0.1) +
      geom_label(x = 1, aes(y = y-5, label = lbl, fill = fill), data = summ, hjust = 0.5, alpha = 0.5) +
      coord_cartesian_panels(panel_limits = lims, clip = c("on", "off", "on")) +
      theme(plot.margin = unit(c(0.5, 0.65 * max(nchar(summ$lbl)), 0.5, 0.5), "char")) +
      scale_fill_discrete(guide = "none")
    

    result2

    Code for facet_grid2 / FacetGrid2 (change from original is mainly a chunk in the middle of the latter's draw_panels function, to allow separate clipping options for different geom layers; everything else is inherited directly from my current version of ggplot2, which is 3.4.2):

    library(rlang)
    
    FacetGrid2 <- ggproto(
      "FacetGrid2", ggplot2::FacetGrid,
      draw_panels = function(panels, layout, x_scales, y_scales, ranges, coord, data, theme, params) {
        if ((params$free$x || params$free$y) && !coord$is_free()) {
          cli::cli_abort("{.fn {snake_class(coord)}} doesn't support free scales")
        }
        
        cols <- which(layout$ROW == 1)
        rows <- which(layout$COL == 1)
        axes <- render_axes(ranges[cols], ranges[rows], coord, theme, transpose = TRUE)
        
        col_vars <- ggplot2:::unique0(layout[names(params$cols)])
        row_vars <- ggplot2:::unique0(layout[names(params$rows)])
        # Adding labels metadata, useful for labellers
        attr(col_vars, "type") <- "cols"
        attr(col_vars, "facet") <- "grid"
        attr(row_vars, "type") <- "rows"
        attr(row_vars, "facet") <- "grid"
        strips <- render_strips(col_vars, row_vars, params$labeller, theme)
        
        aspect_ratio <- theme$aspect.ratio
        if (!is.null(aspect_ratio) && (params$space_free$x || params$space_free$y)) {
          cli::cli_abort("Free scales cannot be mixed with a fixed aspect ratio")
        }
        if (is.null(aspect_ratio) && !params$free$x && !params$free$y) {
          aspect_ratio <- coord$aspect(ranges[[1]])
        }
        if (is.null(aspect_ratio)) {
          aspect_ratio <- 1
          respect <- FALSE
        } else {
          respect <- TRUE
        }
        ncol <- max(layout$COL)
        nrow <- max(layout$ROW)
        
        if (params$space_free$x) {
          ps <- layout$PANEL[layout$ROW == 1]
          widths <- vapply(ps, function(i) diff(ranges[[i]]$x.range), numeric(1))
          panel_widths <- unit(widths, "null")
        } else {
          panel_widths <- rep(unit(1, "null"), ncol)
        }
        if (params$space_free$y) {
          ps <- layout$PANEL[layout$COL == 1]
          heights <- vapply(ps, function(i) diff(ranges[[i]]$y.range), numeric(1))
          panel_heights <- unit(heights, "null")
        } else {
          panel_heights <- rep(unit(1 * abs(aspect_ratio), "null"), nrow)
        }
        
        # changes from here onwards    
        relevant.panel.children <- with(panels[[1]],
                                        which(!grepl("grill|NULL|zeroGrob", childrenOrder)))
        if(length(coord$clip) == 1) {
          panel.layer.grouping <- list(seq_along(panels[[1]]$childrenOrder))
        } else if (length(coord$clip) == length(relevant.panel.children)) {
          panel.layer.grouping <- lapply(relevant.panel.children, function(n) n)
          panel.layer.grouping[[1]] <- seq_len(panel.layer.grouping[[1]])
          panel.layer.grouping[[length(relevant.panel.children)]] <- seq(panel.layer.grouping[[length(relevant.panel.children)]],
                                                                         length(panels[[1]]$childrenOrder))
        } else {
          message("Clipping instruction cannot be matched unambiguously to layers.")
          break()
        }
    
        by.layer.clip.info <- coord$clip
        panel_table <- vector("list", length = length(by.layer.clip.info))
    
        for(i in seq_along(by.layer.clip.info)) {
          panels_by_layer <- lapply(panels, 
                                    function(p) p$children[panel.layer.grouping[[i]]])
          panel_table_by_layer <- matrix(panels_by_layer, nrow = nrow, ncol = ncol, byrow = TRUE)
    
          panel_table_by_layer <- gtable::gtable_matrix(paste("layout", i, sep = "-"), panel_table_by_layer,
                                                        panel_widths, panel_heights, respect = respect, 
                                                        clip = by.layer.clip.info[[i]], 
                                                        z = matrix(1, ncol = ncol, nrow = nrow))
          panel_table[[i]] <- panel_table_by_layer
        }
    
        panel_table_combined <- panel_table[[1]]
        if(length(by.layer.clip.info) > 1) {
          for(i in seq(2, length(by.layer.clip.info))) {
            for(j in seq_len(nrow(panel_table[[i]]))) {
              grob.dimensions <- panel_table[[i]]$layout[j, ]
              panel_table_combined <- gtable::gtable_add_grob(panel_table_combined,
                                                              list(panel_table[[i]]$grobs[[j]]),
                                                              t = grob.dimensions[["t"]],
                                                              l = grob.dimensions[["l"]],
                                                              b = grob.dimensions[["b"]],
                                                              r = grob.dimensions[["r"]],
                                                              z = grob.dimensions[["z"]],
                                                              clip = grob.dimensions[["clip"]],
                                                              name = grob.dimensions[["name"]])
            }
          }
        }
        panel_table <- panel_table_combined
    
        layout.names <- paste0('panel-', rep(seq_len(nrow), ncol), '-', rep(seq_len(ncol), each = nrow))
        if(length(layout.names) == nrow(panel_table$layout)) {
          panel_table$layout$name <- layout.names
        } else {
          panel_table$layout$name <- paste(rep(layout.names, times = length(by.layer.clip.info)),
                                           rep(seq_along(by.layer.clip.info), each = length(layout.names)),
                                           sep = "-")
        }
    
        # no changes after this point
        panel_table <- gtable::gtable_add_col_space(panel_table,
                                            theme$panel.spacing.x %||% theme$panel.spacing)
        panel_table <- gtable::gtable_add_row_space(panel_table,
                                            theme$panel.spacing.y %||% theme$panel.spacing)
        
        # Add axes
        panel_table <- gtable::gtable_add_rows(panel_table, max_height(axes$x$top),     0)
        panel_table <- gtable::gtable_add_rows(panel_table, max_height(axes$x$bottom), -1)
        panel_table <- gtable::gtable_add_cols(panel_table, max_width(axes$y$left),     0)
        panel_table <- gtable::gtable_add_cols(panel_table, max_width(axes$y$right),   -1)
        panel_pos_col <- panel_cols(panel_table)
        panel_pos_rows <- panel_rows(panel_table)
        
        panel_table <- gtable::gtable_add_grob(panel_table, axes$x$top, 1, panel_pos_col$l, clip = "off", name = paste0("axis-t-", seq_along(axes$x$top)), z = 3)
        panel_table <- gtable::gtable_add_grob(panel_table, axes$x$bottom, -1, panel_pos_col$l, clip = "off", name = paste0("axis-b-", seq_along(axes$x$bottom)), z = 3)
        panel_table <- gtable::gtable_add_grob(panel_table, axes$y$left, panel_pos_rows$t, 1, clip = "off", name = paste0("axis-l-", seq_along(axes$y$left)), z = 3)
        panel_table <- gtable::gtable_add_grob(panel_table, axes$y$right, panel_pos_rows$t, -1, clip = "off", name = paste0("axis-r-", seq_along(axes$y$right)), z= 3)
        
        # Add strips
        switch_x <- !is.null(params$switch) && params$switch %in% c("both", "x")
        switch_y <- !is.null(params$switch) && params$switch %in% c("both", "y")
        inside_x <- (theme$strip.placement.x %||% theme$strip.placement %||% "inside") == "inside"
        inside_y <- (theme$strip.placement.y %||% theme$strip.placement %||% "inside") == "inside"
        strip_padding <- grid::convertUnit(theme$strip.switch.pad.grid, "cm")
        panel_pos_col <- panel_cols(panel_table)
        if (switch_x) {
          if (!is.null(strips$x$bottom)) {
            if (inside_x || all(vapply(axes$x$bottom, is.zero, logical(1)))) {
              panel_table <- gtable::gtable_add_rows(panel_table, max_height(strips$x$bottom), -2)
              panel_table <- gtable::gtable_add_grob(panel_table, strips$x$bottom, -2, panel_pos_col$l, clip = "on", name = paste0("strip-b-", seq_along(strips$x$bottom)), z = 2)
            } else {
              panel_table <- gtable::gtable_add_rows(panel_table, strip_padding, -1)
              panel_table <- gtable::gtable_add_rows(panel_table, max_height(strips$x$bottom), -1)
              panel_table <- gtable::gtable_add_grob(panel_table, strips$x$bottom, -1, panel_pos_col$l, clip = "on", name = paste0("strip-b-", seq_along(strips$x$bottom)), z = 2)
            }
          }
        } else {
          if (!is.null(strips$x$top)) {
            if (inside_x || all(vapply(axes$x$top, is.zero, logical(1)))) {
              panel_table <- gtable::gtable_add_rows(panel_table, max_height(strips$x$top), 1)
              panel_table <- gtable::gtable_add_grob(panel_table, strips$x$top, 2, panel_pos_col$l, clip = "on", name = paste0("strip-t-", seq_along(strips$x$top)), z = 2)
            } else {
              panel_table <- gtable::gtable_add_rows(panel_table, strip_padding, 0)
              panel_table <- gtable::gtable_add_rows(panel_table, max_height(strips$x$top), 0)
              panel_table <- gtable::gtable_add_grob(panel_table, strips$x$top, 1, panel_pos_col$l, clip = "on", name = paste0("strip-t-", seq_along(strips$x$top)), z = 2)
            }
          }
        }
        panel_pos_rows <- panel_rows(panel_table)
        if (switch_y) {
          if (!is.null(strips$y$left)) {
            if (inside_y || all(vapply(axes$y$left, is.zero, logical(1)))) {
              panel_table <- gtable::gtable_add_cols(panel_table, max_width(strips$y$left), 1)
              panel_table <- gtable::gtable_add_grob(panel_table, strips$y$left, panel_pos_rows$t, 2, clip = "on", name = paste0("strip-l-", seq_along(strips$y$left)), z = 2)
            } else {
              panel_table <- gtable::gtable_add_cols(panel_table, strip_padding, 0)
              panel_table <- gtable::gtable_add_cols(panel_table, max_width(strips$y$left), 0)
              panel_table <- gtable::gtable_add_grob(panel_table, strips$y$left, panel_pos_rows$t, 1, clip = "on", name = paste0("strip-l-", seq_along(strips$y$left)), z = 2)
            }
          }
        } else {
          if (!is.null(strips$y$right)) {
            if (inside_y || all(vapply(axes$y$right, is.zero, logical(1)))) {
              panel_table <- gtable::gtable_add_cols(panel_table, max_width(strips$y$right), -2)
              panel_table <- gtable::gtable_add_grob(panel_table, strips$y$right, panel_pos_rows$t, -2, clip = "on", name = paste0("strip-r-", seq_along(strips$y$right)), z = 2)
            } else {
              panel_table <- gtable::gtable_add_cols(panel_table, strip_padding, -1)
              panel_table <- gtable::gtable_add_cols(panel_table, max_width(strips$y$right), -1)
              panel_table <- gtable::gtable_add_grob(panel_table, strips$y$right, panel_pos_rows$t, -1, clip = "on", name = paste0("strip-r-", seq_along(strips$y$right)), z = 2)
            }
          }
        }
        panel_table
      }
    )
    
    # only change from facet_grid is the use of FacetGrid2 instead of FacetGrid
    facet_grid2 <- function (rows = NULL, cols = NULL, scales = "fixed", space = "fixed", 
                             shrink = TRUE, labeller = "label_value", as.table = TRUE, 
                             switch = NULL, drop = TRUE, margins = FALSE, facets = lifecycle::deprecated()) {
      if (lifecycle::is_present(facets)) {
        deprecate_warn0("2.2.0", "facet_grid(facets)", "facet_grid(rows)")
        rows <- facets
      }
      if (is.logical(cols)) {
        margins <- cols
        cols <- NULL
      }
      scales <- arg_match0(scales %||% "fixed", c("fixed", "free_x", 
                                                  "free_y", "free"))
      free <- list(x = any(scales %in% c("free_x", "free")), y = any(scales %in% 
                                                                       c("free_y", "free")))
      space <- arg_match0(space %||% "fixed", c("fixed", "free_x", 
                                                "free_y", "free"))
      space_free <- list(x = any(space %in% c("free_x", "free")), 
                         y = any(space %in% c("free_y", "free")))
      if (!is.null(switch) && !switch %in% c("both", "x", "y")) {
        cli::cli_abort("{.arg switch} must be either {.val both}, {.val x}, or {.val y}")
      }
      facets_list <- ggplot2:::grid_as_facets_list(rows, cols)
      labeller <- ggplot2:::check_labeller(labeller)
      ggproto(NULL, FacetGrid2, shrink = shrink, 
              params = list(rows = facets_list$rows, 
                            cols = facets_list$cols, margins = margins, free = free, 
                            space_free = space_free, labeller = labeller, as.table = as.table, 
                            switch = switch, drop = drop))
    }
    

    Disclaimer: I haven't tested this for other use cases because I haven't had a need for it, so... caveat emptor. :)