Legend and facet spacing (#94)

* Add par2(lmar) option * Catch after par2 update * First stab at integrating fixed margins * clean up * Still testing, but better defaults * document * Fix first plot spacing - Need to set par(mar) margins first. - Also consolidate outer right and left code logic. - Clean up too. * clean up * Outer bottom and top * Adjust for sub if legend = "bottom!" * Better facet support with new legend spacing logic * Bump roxygen2 version * Tweak plot2 lmar * Legend fully in outer margin (incl. inside gap) * Better facet logic for consistency across facet types - Principled gaps between facets - Overall plot region matched to single (no facet) plot * Clean up old facet logic - Better internal comments too. * document * Fixed "left!" and "right!" insets * Fix "bottom!" and "top!" support * Better catch for recursive "top!" calls * update tests * Document par2 - Also add fmar to par2 options * Remove grid from par2 for the moment - Reinstate after this PR is finished * better catch for custom user mfrow cases * Update README and vignette * Add NEWS items * Bump version * Add more legend tests * Add lmar tests * Add more facet tests - Specifically 2 by x cases * Fix fmar bug when passed through facet.args * Add fmar tests * Fix wording about facet margins * export draw_legend and update namespace * Add README.qmd to .Rbuildignore * Tweak facet spacing logic for >=3 case (i.e., exception for 2x2 case) * Update tests and clean up * Better documentation of fmar spacing logic
grantmcdermott · Jan 21, 2024 · 2dcae14 · 2dcae14
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diff --git a/.Rbuildignore b/.Rbuildignore
@@ -3,6 +3,7 @@
 ^\.Rproj\.user$
 ^_EXAMPLES$
 ^README\.Rmd$
+^README\.qmd$
 ^README\.html$
 ^_pkgdown\.yml$
 ^docs$

diff --git a/DESCRIPTION b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: plot2
 Type: Package
 Title: Lightweight extension of base R plot
-Version: 0.0.3.9014
+Version: 0.0.3.9015
 Authors@R: 
   c(
     person(
@@ -53,7 +53,7 @@ Suggests:
 Remotes: 
   etiennebacher/altdoc
 Encoding: UTF-8
-RoxygenNote: 7.2.3.9000
+RoxygenNote: 7.3.0
 URL: https://grantmcdermott.com/plot2/,
     http://grantmcdermott.com/plot2/
 BugReports: https://github.com/grantmcdermott/plot2/issues
diff --git a/NAMESPACE b/NAMESPACE
@@ -3,6 +3,8 @@
 S3method(plot2,default)
 S3method(plot2,density)
 S3method(plot2,formula)
+export(draw_legend)
+export(par2)
 export(plot2)
 importFrom(grDevices,adjustcolor)
 importFrom(grDevices,extendrange)
@@ -18,6 +20,7 @@ importFrom(graphics,arrows)
 importFrom(graphics,axis)
 importFrom(graphics,box)
 importFrom(graphics,grconvertX)
+importFrom(graphics,grconvertY)
 importFrom(graphics,lines)
 importFrom(graphics,mtext)
 importFrom(graphics,par)

diff --git a/NEWS.md b/NEWS.md
@@ -1,6 +1,6 @@
 # News
 
-##  0.0.3.914 (development version)
+##  0.0.3.915 (development version)
 
 Website:
 
@@ -26,7 +26,13 @@ existing plot window. (#60 @grantmcdermott)
 - `plot2` gains a new `facet` argument for drawing faceted plots. Users can
 override the default square arrangement by passing the desired number of facet
 rows or columns to the companion `facet.args` helper function. Facets can be
-combined with `by` grouping, or used on their own. (#83, #91 @grantmcdermott)
+combined with `by` grouping, or used on their own. (#83, #91, #94
+@grantmcdermott)
+- Users can now control `plot2`-specific graphical parameters globally via
+the new `par2()` function (which is modeled on the base `par()` function). At
+the moment only a subset of global parameters, mostly related to legend and
+facet behaviour, are exposed in `par2`. But users can expect that more will be
+added in future releases. (#33, #94 @grantmcdermott)
 
 Bug fixes:
 
@@ -37,6 +43,17 @@ e.g. `plot2(rnorm(100)`. (#52 etiennebacher)
 - Interval plots like ribbons, errorbars, and pointranges are now correctly
 plotted even if a y variable isn't specified. (#54 @grantmcdermott)
 - Correctly label date-time axes. (#77 @grantmcdermott and @zeileis)
+- Improved consistency of legend and facet margins across different plot types
+and placement, via the new `lmar` and `fmar` arguments of `par2()`. The default
+legend margin is `par2(lmar = c(1,0, 0.1)`, which means that there is 1.0 line
+of padding between the legend and the plot region (inside margin) and 0.1 line 
+of padding between the legend and edge of the graphics device (outer margin).
+Similarly, the default facet padding is `par2(fmar = c(1,1,1,1)`, which means
+that there is a single line of padding around each side of the individual
+facets. Users can override these defaults by passing numeric vectors of the
+appropriate length to `par2()`. For example, `par2(lmar = c(0,0.1)` would shrink
+the inner gap between the legend and plot region to zero, but leave the small
+outer gap to outside of the graphics device unchanged. (#94 @grantmcdermott)
 
 ##  0.0.3
 

diff --git a/R/draw_legend.R b/R/draw_legend.R
@@ -14,7 +14,64 @@
 #' @param col Plotting colour(s), passed down from `plot2`.
 #' @param bg Plotting character background fill colour(s), passed down from `plot2`.
 #' @param cex Plotting character expansion(s), passed down from `plot2`.
-#' @param new_plot Should we be calling plot.new internally? 
+#' @param lmar Legend margins (in lines). Should be a numeric vector of the form
+#'   `c(inner, outer)`, where the first number represents the "inner" margin
+#'   between the legend and the plot, and the second number represents the
+#'   "outer" margin between the legend and edge of the graphics device. If no
+#'   explicit value is provided by the user, then reverts back to `par2("lmar")`
+#'   for which the default values are `c(1.0, 0.1)`.
+#' @param has_sub Logical. Does the plot have a sub-caption. Only used if
+#'   keyword position is "bottom!", in which case we need to bump the legend
+#'   margin a bit further.
+#' @param new_plot Should we be calling plot.new internally?
+#' @examples
+#' 
+#' oldmar = par("mar")
+#' 
+#' draw_legend(
+#'   legend = "right!", ## default (other options incl, "left(!)", ""bottom(!)", etc.)
+#'   legend.args = list(title = "Key", bty = "o"),
+#'   lgnd_labs = c("foo", "bar"),
+#'   type = "p",
+#'   pch = 21:22,
+#'   col = 1:2
+#' )
+#' 
+#' # The legend is placed in the outer margin...
+#' box("figure", col = "cyan", lty = 4)
+#' # ... and the plot is proportionally adjusted against the edge of this
+#' # margin.
+#' box("plot")
+#' # You can add regular plot objects per normal now
+#' plot.window(xlim = c(1,10), ylim = c(1,10))
+#' points(1:10)
+#' points(10:1, pch = 22, col = "red")
+#' axis(1); axis(2)
+#' # etc.
+#' 
+#' # Important: A side effect of draw_legend is that the inner margins have been
+#' # adjusted. (Here: The right margin, since we called "right!" above.)
+#' par("mar")
+#' 
+#' # To reset you should call `dev.off()` or just reset manually.
+#' par(mar = oldmar)
+#' 
+#' # Note that the inner and outer margin of the legend itself can be set via
+#' # the `lmar` argument. (This can also be set globally via
+#' # `par2(lmar = c(inner, outer))`.)
+#' draw_legend(
+#'   legend.args = list(title = "Key", bty = "o"),
+#'   lgnd_labs = c("foo", "bar"),
+#'   type = "p",
+#'   pch = 21:22,
+#'   col = 1:2,
+#'   lmar = c(0, 0.1) ## set inner margin to zero
+#' )
+#' box("figure", col = "cyan", lty = 4)
+#' 
+#' par(mar = oldmar)
+#' 
+#' @export
 draw_legend = function(
     legend = NULL,
     legend.args = NULL,
@@ -26,10 +83,21 @@ draw_legend = function(
     col = NULL,
     bg = NULL,
     cex = NULL,
+    lmar = NULL,
+    has_sub = FALSE,
     new_plot = TRUE
 ) {
 
-  w = h = outer_right = outer_bottom = NULL
+  if (is.null(lmar)) {
+    lmar = par2("lmar")
+  } else {
+    if (!is.numeric(lmar) || length(lmar)!=2) stop ("lmar must be a numeric of length 2.")
+  }
+
+  soma = outer_right = outer_bottom = NULL
+
+  #
+  ## legend args ----
 
   if (is.null(legend)) {
     legend.args[["x"]] = "right!"
@@ -88,28 +156,59 @@ draw_legend = function(
     legend.args[["legend"]] = lgnd_labs
   }
 
-  # Catch to avoid recursive offsets, e.g., repeated plot2 calls with
+  #
+  ## legend placement ----
+
+  ooma = par("oma")
+  omar = par("mar")
+  topmar_epsilon = 0.1
+
+  # Catch to avoid recursive offsets, e.g. repeated plot2 calls with
   # "bottom!" legend position.
+
+  ## restore inner margin defaults
+  ## (in case the plot region/margins were affected by the preceding plot2 call)
+  if (any(ooma != 0)) {
+    if ( ooma[1] != 0 & omar[1] == par("mgp")[1] + 1*par("cex.lab") ) omar[1] = 5.1
+    if ( ooma[2] != 0 & omar[2] == par("mgp")[1] + 1*par("cex.lab") ) omar[2] = 4.1
+    if ( ooma[3] == topmar_epsilon & omar[3] != 4.1 ) omar[3] = 4.1
+    if ( ooma[4] != 0 & omar[4] == 0 ) omar[4] = 2.1
+    par(mar = omar)
+  }
+  ## restore outer margin defaults
   par(omd = c(0,1,0,1))
+  ooma = par("oma")
+
 
-  ## Legend to outer side of plot
+  ## Legend to outer side (either right or left) of plot
   if (grepl("right!$|left!$", legend.args[["x"]])) {
 
     outer_right = grepl("right!$", legend.args[["x"]])
 
-    # Margins of the plot (the first is the bottom margin)
+    ## Switch position anchor (we'll adjust relative to the _opposite_ side below)
+    if (outer_right) legend.args[["x"]] = gsub("right!$", "left", legend.args[["x"]])
+    if (!outer_right) legend.args[["x"]] = gsub("left!$", "right", legend.args[["x"]])
+
+    ## We have to set the inner margins of the plot before the (fake) legend is
+    ## drawn, otherwise the inset calculation---which is based in the legend
+    ## width---will be off the first time.
     if (outer_right) {
-      par(mar=c(par("mar")[1:3], 0.1)) # remove right inner margin space
-    } else if (par("mar")[4]==0.1) {
-      par(mar=c(par("mar")[1:3], 2.1)) # revert right margin if outer left
+      # par(mar=c(par("mar")[1:3], 0)) ## Set rhs inner mar to zero
+      omar[4] = 0 ## TEST
+    } else {
+      # For outer left we have to account for the y-axis label too, which
+      # requires additional space
+      # par(mar=c(
+      #   par("mar")[1],
+      #   par("mgp")[1] + 1*par("cex.lab"),
+      #   par("mar")[3:4]
+      #   ))
+      omar[2] = par("mgp")[1] + 1*par("cex.lab") ## TEST
     }
+    par(mar = omar) ## TEST
 
     if (isTRUE(new_plot)) plot.new()
 
-    ## Switch position anchor (we'll adjust relative to the _opposite_ side below)
-    if (outer_right) legend.args[["x"]] = gsub("right!$", "left", legend.args[["x"]])
-    if (!outer_right) legend.args[["x"]] = gsub("left!$", "right", legend.args[["x"]])
-
     legend.args[["horiz"]] = FALSE
 
     # "draw" fake legend
@@ -119,33 +218,62 @@ draw_legend = function(
       keep.null = TRUE
     )
     fklgnd = do.call("legend", fklgnd.args)
-    # calculate side margin width in ndc
-    w = grconvertX(fklgnd$rect$w, to="ndc") - grconvertX(0, to="ndc")
-    ## differing adjustments depending on side
+
+    # calculate outer margin width in lines
+    soma = grconvertX(fklgnd$rect$w, to="lines") - grconvertX(0, to="lines")
+    # Add legend margins to the outer margin
+    soma = soma + sum(lmar)
+    # ooma = par("oma")  ## TEST (comment)
+    ## differing outer margin adjustments depending on side
     if (outer_right) {
-      w = w*1.5
-      par(omd = c(0, 1-w, 0, 1))
-      legend.args[["inset"]] = c(1.025, 0)
+      ooma[4] = soma
     } else {
-      w = w + grconvertX(par("mgp")[1], from = "lines", to = "ndc") # extra space for y-axis title
-      par(omd = c(w, 1, 0, 1))
-      legend.args[["inset"]] = c(1+w, 0)
+      ooma[2] = soma
+    }
+    par(oma = ooma)
+
+    # determine legend inset
+    inset = grconvertX(lmar[1], from="lines", to="npc") - grconvertX(0, from = "lines", to = "npc")
+    if (isFALSE(outer_right)) {
+      # extra space needed for "left!" b/c of lhs inner margin
+      inset_bump = grconvertX(par("mar")[2], from = "lines", to = "npc") - grconvertX(0, from = "lines", to = "npc")
+      inset = inset + inset_bump
     }
+    # GM: The legend inset spacing only works _exactly_ if we refresh the plot
+    # area. I'm not sure why (and it works properly if we use the same
+    # parameters manually while debugging), but this hack seems to work.
+    par(new = TRUE)
+    plot.new()
+    par(new = FALSE)
+    # Finally, set the inset as part of the legend args.
+    legend.args[["inset"]] = c(1+inset, 0)
 
     ## Legend at the outer top or bottom of plot
   } else if (grepl("bottom!$|top!$", legend.args[["x"]])) {
 
     outer_bottom = grepl("bottom!$", legend.args[["x"]])
 
-    # Catch to reset right margin if previous legend position was "right!"
-    if (par("mar")[4]== 0.1) par(mar=c(par("mar")[1:3], 2.1)) 
-
-    if (isTRUE(new_plot)) plot.new()
-
     ## Switch position anchor (we'll adjust relative to the _opposite_ side below)
     if (outer_bottom) legend.args[["x"]] = gsub("bottom!$", "top", legend.args[["x"]])
     if (!outer_bottom) legend.args[["x"]] = gsub("top!$", "bottom", legend.args[["x"]])
 
+    ## We have to set the inner margins of the plot before the (fake) legend is
+    ## drawn, otherwise the inset calculation---which is based in the legend
+    ## width---will be off the first time.
+    if (outer_bottom) {
+      omar[1] = par("mgp")[1] + 1*par("cex.lab") ## TEST
+      if (isTRUE(has_sub)) omar[1] = omar[1] + 1*par("cex.sub") ## TEST 
+    } else {
+      ## For "top!", the logic is slightly different: We don't expand the outer
+      ## margin b/c we need the legend to come underneath the main title. So
+      ## we rather expand the existing inner margin.
+      ooma[3] = ooma[3] + topmar_epsilon ## TESTING
+      par(oma = ooma)
+    }
+    par(mar = omar)
+
+    if (isTRUE(new_plot)) plot.new()
+
     legend.args[["horiz"]] = TRUE
 
     # Catch for horizontal ribbon legend spacing
@@ -160,24 +288,45 @@ draw_legend = function(
     # "draw" fake legend
     fklgnd.args = utils::modifyList(
       legend.args,
-      list(x = 0, y = 0, plot = FALSE),
+      # list(x = 0, y = 0, plot = FALSE),
+      list(plot = FALSE),
       keep.null = TRUE
     )
     fklgnd = do.call("legend", fklgnd.args)
-    # calculate bottom margin height in ndc
-    h = grconvertX(fklgnd$rect$h, to="ndc") - grconvertX(0, to="ndc")
-    ## differing adjustments depending on side
+
+    # calculate outer margin width in lines
+    soma = grconvertY(fklgnd$rect$h, to="lines") - grconvertY(0, to="lines")
+    # Add legend margins to outer margin
+    soma = soma + sum(lmar)
+    ## differing outer margin adjustments depending on side
     if (outer_bottom) {
-      legend.args[["inset"]] = c(0, 1+2*h)
-      par(omd = c(0,1,0+h,1))
+      ooma[1] = soma
+    } else {
+      omar[3] = omar[3] + soma - topmar_epsilon
+      par(mar = omar)
+    }
+    par(oma = ooma)
+
+    # determine legend inset
+    inset = grconvertY(lmar[1], from="lines", to="npc") - grconvertY(0, from="lines", to="npc")
+    if (isTRUE(outer_bottom)) {
+      # extra space needed for "bottom!" b/c of lhs inner margin
+      inset_bump = grconvertY(par("mar")[1], from="lines", to="npc") - grconvertY(0, from="lines", to="npc")
+      inset = inset + inset_bump
     } else {
-      legend.args[["inset"]] = c(0, 1)
-      par(omd = c(0,1,0,1-h))
+      epsilon_bump = grconvertY(topmar_epsilon, from="lines", to="npc") - grconvertY(0, from="lines", to="npc")
+      inset = inset + epsilon_bump
     }
+    # GM: The legend inset spacing only works _exactly_ if we refresh the plot
+    # area. I'm not sure why (and it works properly if we use the same
+    # parameters manually while debugging), but this hack seems to work.
+    par(new = TRUE)
+    plot.new()
+    par(new = FALSE)
+    # Finally, set the inset as part of the legend args.
+    legend.args[["inset"]] = c(0, 1+inset)
 
   } else {
-    # Catch to reset right margin if previous legend position was "right!"
-    if (par("mar")[4] == 0.1) par(mar=c(par("mar")[1:3], par("mar")[2]-2)) 
     legend.args[["inset"]] = 0
     if (isTRUE(new_plot)) plot.new()
   }