Merge pull request #993 from noamross/feature/panel_on_top

New theme option to put panel/grid on top of data

Author: hadley

NEWS

@@ -101,6 +101,10 @@ ggplot2 1.0.1.9000
   one place rather than having to navigate through multiple pages. Use
   of `qplot()` in examples has been minimised (#1123, @hrbrmstr)
 
+* new theme setting `panel.ontop` (logical) allows placing background elements
+  (e.g., gridlines) on top of data. Usually used with blank or transparent
+  `panel.background`.  (@noamross. #551)
+
 ggplot2 1.0.1
 ----------------------------------------------------------------
 

R/facet-grid-.r

@@ -365,7 +365,12 @@ facet_panels.grid <- function(facet, panel, coord, theme, geom_grobs) {
     bg <- coord_render_bg(coord, panel$ranges[[i]], theme)
 
     geom_grobs <- lapply(geom_grobs, "[[", i)
-    panel_grobs <- c(list(bg), geom_grobs, list(fg))
+
+    if(theme$panel.ontop) {
+      panel_grobs <- c(geom_grobs, list(bg), list(fg))
+    } else {
+      panel_grobs <- c(list(bg), geom_grobs, list(fg))
+    }
 
     gTree(children = do.call("gList", panel_grobs))
   })

R/facet-null.r

@@ -45,7 +45,12 @@ facet_render.null <- function(facet, panel, coord, theme, geom_grobs) {
 
   # Flatten layers - we know there's only one panel
   geom_grobs <- lapply(geom_grobs, "[[", 1)
-  panel_grobs <- c(list(bg), geom_grobs, list(fg))
+
+  if(theme$panel.ontop) {
+    panel_grobs <- c(geom_grobs, list(bg), list(fg))
+  } else {
+    panel_grobs <- c(list(bg), geom_grobs, list(fg))
+  }
 
   panel_grob <- gTree(children = do.call("gList", panel_grobs))
   axis_h <- coord_render_axis_h(coord, range, theme)

R/facet-wrap.r

@@ -202,7 +202,12 @@ facet_panels.wrap <- function(facet, panel, coord, theme, geom_grobs) {
     bg <- coord_render_bg(coord, panel$ranges[[i]], theme)
 
     geom_grobs <- lapply(geom_grobs, "[[", i)
-    panel_grobs <- c(list(bg), geom_grobs, list(fg))
+
+    if(theme$panel.ontop) {
+      panel_grobs <- c(geom_grobs, list(bg), list(fg))
+    } else {
+      panel_grobs <- c(list(bg), geom_grobs, list(fg))
+    }
 
     ggname(paste("panel", i, sep = "-"),
       gTree(children = do.call("gList", panel_grobs)))

R/theme-defaults.r

@@ -102,6 +102,7 @@ theme_grey <- function(base_size = 12, base_family = "") {
     panel.margin =       unit(0.25, "lines"),
     panel.margin.x =     NULL,
     panel.margin.y =     NULL,
+    panel.ontop    =     FALSE,
 
     strip.background =   element_rect(fill = "grey80", colour = NA),
     strip.text.x =       element_text(),

R/theme-elements.r

@@ -272,6 +272,7 @@ el_def <- function(class = NULL, inherit = NULL, description = NULL) {
   panel.grid.major.y  = el_def("element_line", "panel.grid.major"),
   panel.grid.minor.x  = el_def("element_line", "panel.grid.minor"),
   panel.grid.minor.y  = el_def("element_line", "panel.grid.minor"),
+  panel.ontop         = el_def("logical"),
 
   strip.background    = el_def("element_rect", "rect"),
   strip.text.x        = el_def("element_text", "strip.text"),

R/theme.r

@@ -157,6 +157,9 @@ print.theme <- function(x, ...) str(x)
 #'                    (\code{element_line}; inherits from \code{panel.grid.minor}) \cr
 #'   panel.grid.minor.y \tab horizontal minor grid lines
 #'                    (\code{element_line}; inherits from \code{panel.grid.minor}) \cr
+#'   panel.ontop        \tab option to place the panel (background, gridlines)
+#'                           over the data layers.  Usually used with a transparent
+#'                           or blank \code{panel.background}. (\code{logical}) \cr
 #'
 #'   plot.background  \tab background of the entire plot
 #'                    (\code{element_rect}; inherits from \code{rect}) \cr
@@ -293,6 +296,17 @@ print.theme <- function(x, ...) str(x)
 #' k + theme(panel.margin = unit(5, "lines"))
 #' k + theme(panel.margin.y = unit(0, "lines"))
 #'
+#' # Put gridlines on top
+#' meanprice <- tapply(diamonds$price, diamonds$cut, mean)
+#' cut <- factor(levels(diamonds$cut), levels = levels(diamonds$cut))
+#' df <- data.frame(meanprice, cut)
+#' g <- ggplot(df, aes(cut, meanprice)) + geom_bar(stat = "identity")
+#' g + geom_bar(stat = "identity") +
+#'     theme(panel.background=element_blank(),
+#'           panel.grid.major.x=element_blank(),
+#'           panel.grid.minor.x = element_blank(),
+#'           panel.grid.minor.y=element_blank(),
+#'           panel.ontop=TRUE)
 #'
 #' # Modify a theme and save it
 #' mytheme <- theme_grey() + theme(plot.title = element_text(colour = "red"))
@@ -410,7 +424,7 @@ add_theme <- function(t1, t2, t2name) {
       # If x is NULL or element_blank, then just assign it y
       x <- y
     } else if (is.null(y) || is.character(y) || is.numeric(y) ||
-               inherits(y, "element_blank")) {
+               is.logical(y) || inherits(y, "element_blank")) {
       # If y is NULL, or a string or numeric vector, or is element_blank, just replace x
       x <- y
     } else {

man/theme.Rd

@@ -132,6 +132,9 @@ The individual theme elements are:
                    (\code{element_line}; inherits from \code{panel.grid.minor}) \cr
   panel.grid.minor.y \tab horizontal minor grid lines
                    (\code{element_line}; inherits from \code{panel.grid.minor}) \cr
+  panel.ontop        \tab option to place the panel (background, gridlines)
+                          over the data layers.  Usually used with a transparent
+                          or blank \code{panel.background}. (\code{logical}) \cr
 
   plot.background  \tab background of the entire plot
                    (\code{element_rect}; inherits from \code{rect}) \cr
@@ -253,6 +256,17 @@ k + theme(strip.text.x = element_text(colour = "red", angle = 45, size = 10,
 k + theme(panel.margin = unit(5, "lines"))
 k + theme(panel.margin.y = unit(0, "lines"))
 
+# Put gridlines on top
+meanprice <- tapply(diamonds$price, diamonds$cut, mean)
+cut <- factor(levels(diamonds$cut), levels = levels(diamonds$cut))
+df <- data.frame(meanprice, cut)
+g <- ggplot(df, aes(cut, meanprice)) + geom_bar(stat = "identity")
+g + geom_bar(stat = "identity") +
+    theme(panel.background=element_blank(),
+          panel.grid.major.x=element_blank(),
+          panel.grid.minor.x = element_blank(),
+          panel.grid.minor.y=element_blank(),
+          panel.ontop=TRUE)
 
 # Modify a theme and save it
 mytheme <- theme_grey() + theme(plot.title = element_text(colour = "red"))