Fix aspect ratio in facet_wrap. First pass at improved coord_equal - modulo panel size problem

Author: hadley

NEWS

@@ -37,4 +37,7 @@ ggplot2 0.8.5 (2009-XX-XX) ----------------------------------------
 * legends will only merge if both the title and all labels are the same.
   (Fixes #16)
 * Fix for bug #19: Legend with three constraints doesn't work 
-* Legend: correctly calculate label widths for all font sizes.  (Fixes #38)
+* Legend: correctly calculate label widths for all font sizes.  (Fixes #38)
+* facet_wrap: now sets aspect ratio correctly
+* coord_equal: when ratio = NULL (the default), will adjust the aspect ratio
+  of the plot, rather than trying to extend the shortest scale.

R/coord-.r

@@ -34,6 +34,10 @@ Coord <- proto(TopLevel, expr={
     )
   }
 
+  compute_aspect <- function(., ranges) {
+    NULL
+  }
+  
   labels <- function(., scales) {
     scales
   }

R/coord-cartesian-equal.r

@@ -1,7 +1,7 @@
 CoordEqual <- proto(CoordCartesian, {
 
-  new <- function(., ratio=1) {
-    list(.$proto(ratio = ratio), opts(aspect.ratio = ratio))
+  new <- function(., ratio = NULL) {
+    .$proto(ratio = ratio)
   }
 
   compute_ranges <- function(., scales) {
@@ -13,6 +13,12 @@ CoordEqual <- proto(CoordCartesian, {
 
     .super$compute_ranges(., scales)
   }
+  
+  compute_aspect <- function(., ranges) {
+    if (!is.null(.$ratio)) return(.$ratio)
+    
+    diff(ranges$y.range) / diff(ranges$x.range)
+  }
 
   # Documentation -----------------------------------------------
 
@@ -23,8 +29,12 @@ CoordEqual <- proto(CoordCartesian, {
   details <- "<p>An equal scale coordinate system plays a similar role to ?eqscplot in MASS, but it works for all types of graphics, not just scatterplots.</p>\n<p>This coordinate system has one parameter, <code>ratio</code>, which specifies the ratio between the x and y scales. An aspect ratio of two means that the plot will be twice as high as wide.  An aspection ratio of 1/2 means that the plot will be twice as wide as high.   By default, the aspect.ratio of the plot will also be set to this value.</p>\n"
 
   examples <- function(.) {
-    # coord_equal ensures that the ranges of axes are equal to the
-    # specified ratio (1 by default, indicating equal ranges).
+    # ratio = NULL, the default, will modify the aspect ratio of the plot
+    # to 
+    qplot(mpg, wt, data = mtcars) + coord_equal()
+
+    # when ratio = a specific number, ensures that the ranges of axes are
+    # equal to the specified ratio by expanding the smallest axis
 
     qplot(mpg, wt, data = mtcars) + coord_equal(ratio = 1)
     qplot(mpg, wt, data = mtcars) + coord_equal(ratio = 5)
@@ -44,7 +54,9 @@ CoordEqual <- proto(CoordCartesian, {
 # @arguments y limits
 # @arguments desired ratio between x and y ranges
 # @keywords internal
-equal_ranges <- function(xlim, ylim, ratio = 1) {
+equal_ranges <- function(xlim, ylim, ratio = NULL) {
+  if (is.null(ratio)) return(list(x = xlim, y = ylim))
+
   xr <- diff(xlim)
   yr <- diff(ylim)
 

R/facet-grid-.r

@@ -43,7 +43,18 @@ FacetGrid <- proto(Facet, {
 
   # Create grobs for each component of the panel guides
   add_guides <- function(., data, panels_grob, coord, theme) {
+
     aspect_ratio <- theme$aspect.ratio
+    
+    # If user hasn't set aspect ratio, and we have fixed scales, then
+    # ask the coordinate system if it wants to specify one
+    if (is.null(aspect_ratio) && !.$free$x && !.$free$y) {
+      xscale <- .$scales$x[[1]]
+      yscale <- .$scales$y[[1]]
+      ranges <- coord$compute_ranges(list(x = xscale, y = yscale))
+      aspect_ratio <- coord$compute_aspect(ranges)
+    }
+    
     if (is.null(aspect_ratio)) {
       aspect_ratio <- 1
       respect <- FALSE

R/facet-wrap.r

@@ -44,9 +44,25 @@ FacetWrap <- proto(Facet, {
 
   # Create grobs for each component of the panel guides
   add_guides <- function(., data, panels_grob, coord, theme) {
+
     aspect_ratio <- theme$aspect.ratio
-    if (is.null(aspect_ratio)) aspect_ratio <- 1
 
+    # If user hasn't set aspect ratio, and we have fixed scales, then
+    # ask the coordinate system if it wants to specify one
+    if (is.null(aspect_ratio) && !.$free$x && !.$free$y) {
+      xscale <- .$scales$x[[1]]
+      yscale <- .$scales$y[[1]]
+      ranges <- coord$compute_ranges(list(x = xscale, y = yscale))
+      aspect_ratio <- coord$compute_aspect(ranges)
+    }
+    
+    if (is.null(aspect_ratio)) {
+      aspect_ratio <- 1
+      respect <- FALSE
+    } else {
+      respect <- TRUE
+    }
+        
     n <- length(.$scales$x)
 
     axes_h <- matrix(list(), nrow = 1, ncol = n)
@@ -88,7 +104,7 @@ FacetWrap <- proto(Facet, {
     panelsGrid <- grobGrid(
       "panel", panels, nrow = nrow, ncol = ncol,
       heights = 1 * aspect_ratio, widths = 1,
-      as.table = .$as.table
+      as.table = .$as.table, respect = respect
     )
 
     strips <- .$labels_default(.$facet_levels, theme)