fails with ggh4x::facet_wrap2(trim_blank=FALSE)

[r2evans]

When using ggh4x::facet_wrap2 in a subplot and combining, it works only if trim_blank=TRUE (the default); if I try to preserve blanks then it presents a blank canvas.

library(ggplot2)
library(patchwork)
spldat <- data.frame(x=c(1, 1, 2), y = c(1, 2, 2)) |> split(~ x)
plots <- lapply(spldat, \(dat) ggplot(dat, aes(x, y)) + geom_point() +
                                 ggh4x::facet_wrap2(y ~ ., ncol = 2, trim_blank = TRUE))
Reduce(`/`, plots)

plots <- lapply(spldat, \(dat) ggplot(dat, aes(x, y)) + geom_point() +
                                 ggh4x::facet_wrap2(y ~ ., ncol = 2, trim_blank = FALSE))
Reduce(`/`, plots)

(empty for me)

plots[[1]]
plots[[2]]

session info

xfun::session_info("patchwork")
# R version 4.4.3 (2025-02-28)
# Platform: aarch64-apple-darwin20
# Running under: macOS Sequoia 15.5
# Locale: en_US.UTF-8 / en_US.UTF-8 / en_US.UTF-8 / C / en_US.UTF-8 / en_US.UTF-8
# Package version:
#   cli_3.6.5          farver_2.1.2       ggplot2_3.5.2      glue_1.8.0         graphics_4.4.3     grDevices_4.4.3    grid_4.4.3         gtable_0.3.6      
#   isoband_0.2.7      labeling_0.4.3     lattice_0.22.6     lifecycle_1.0.4    magrittr_2.0.3     MASS_7.3.64        Matrix_1.7.2       methods_4.4.3     
#   mgcv_1.9.1         nlme_3.1.167       patchwork_1.3.1    pillar_1.10.2      pkgconfig_2.0.3    R6_2.6.0           RColorBrewer_1.1.3 rlang_1.1.6       
#   scales_1.4.0       splines_4.4.3      stats_4.4.3        tibble_3.3.0       utf8_1.2.4         utils_4.4.3        vctrs_0.6.5        viridisLite_0.4.2 
#   withr_3.0.2       

[teunbrand]

It might be that one of the assumptions of patchwork is to have a grob present (even if it is a zeroGrob()) at a panel position, whereas this is not the case with ggh4x::facet_wrap2(trim_blank = FALSE). It might be more appropriate for ggh4x to replace the empty panels with zeroGrob()s than to remove the panels.

[r2evans]

I figured it'd be something special with the empty space.

[r2evans]

Any traction here in patchwork or in ggh4x#202? @teunbrand

[teunbrand]

I explored this problem a while ago but haven't found a satisfactory solution. Leaving in dummy grobs to satisfy the gtable assumptions would disrupt the current mechanism too much for me to commit to that.

[r2evans]

For the record (future me + anybody else who may be interested, until something more "proper" may be implemented), an interim solution for me is to use ggplot2::facet_wrap() for the normal plot, and add another similar plot with the correct number of panes with theme_void() (completely empty). It's imperfect (the pane alignment is off a little in some of my plots though not below), but it's workable for now.

library(ggplot2)
library(patchwork)
want_cols <- 6
gg2 <- ggplot(mtcars, aes(mpg,disp)) + geom_point() + facet_wrap(vs + gear ~ ., ncol = want_cols)
gg1a <- ggplot(mtcars, aes(mpg,disp)) + geom_point() + facet_wrap(cyl ~ ., ncol = want_cols)
(need_cols <- (want_cols - length(unique(ggplot_build(gg1a)$layout$layout$PANEL))))
# [1] 3
(facet_vars <- names(gg1a$facet$params$facets))
# [1] "cyl"
gg1b <- merge(
  subset(gg1a$data[1,], select = setdiff(names(gg1a$data), facet_vars)),
  as.data.frame(lapply(setNames(nm=facet_vars), function(z) strrep(" ", 1:need_cols))),
  by = NULL
  ) |>
  ggplot() + 
  facet_wrap(vars(!!!lapply(facet_vars, as.symbol)), ncol = want_cols) +
  theme_void()
(gg1a + gg1b) / gg2