[R] ggplot legend consolidation

[hadley wickham]

Sorry, I should have mentioned that get_legend won't work on the plots
that you are actually plotting - you have turned their legends off!
You'll need a plot which isn't plotted, but is used to produce the
legends.

Hadley

On 9/10/07, Te, Kaom <Kaom.Te at schwab.com> wrote:
> Hi Hadley,
>
> I just tried out your suggestion, but it does not look like the
> get_legends function is working correctly. Instead of returning a grob
> back to me it returns NULL.
>
> Here is my modified code and the results of running it.
>
> Any help would be appreciated. I believe that once I can get the legend
> in grob form then I can figure out how to deconstruct it myself.
>
> Thanks,
> Kaom
>
> > p.legend <- get_legends(p)
> > grid.draw(p.legend)
> Error in grid.draw(p.legend) : no applicable method for "grid.draw"
> > p.legend
> NULL
> >
>
> -------------------------------------------- BEGIN CODE
> ## Obtained from http://pastie.textmate.org/95755
> get_legends <- function(plot) {
>   if (length(plot$layers) == 0) stop("No layers to plot", call.=FALSE)
>
>   # Apply function to layer and matching data
>   dlapply <- function(f) mapply(f, data, layers, SIMPLIFY=FALSE)
>
>   plot <- plot_clone(plot)
>   layers <- plot$layers
>   scales <- plot$scales
>   facet <- plot$facet
>
>   cs <- plot$coordinates
>
>   # Evaluate aesthetics
>   data <- lapply(layers, function(x) x$make_aesthetics(plot))
>
>   # Facet
>   data <- mapply(function(d, p) facet$stamp_data(d), data, layers,
> SIMPLIFY=FALSE)
>   # Transform scales where possible.  Also need to train so statisics
>   # (e.g. stat_smooth) have access to info
>   data <- dlapply(function(d, p) p$scales_transform(d, scales))
>   dlapply(function(d, p) p$scales_train(d, scales))
>
>   # Apply statistics
>   data <- dlapply(function(d, p) p$calc_statistics(d, scales))
>   data <- dlapply(function(d, p) p$map_statistics(d, plot))
>
>   # Adjust position before scaling
>   data <- dlapply(function(d, p) p$adjust_position(d, scales, "before"))
>   # Transform, train and map scales
>   # data <- dlapply(function(d, p) p$scales_transform(d, scales))
>   dlapply(function(d, p) p$scales_train(d, scales, adjust=TRUE))
>   data <- dlapply(function(d, p) p$scales_map(d, scales))
>
>   # Adjust position after scaling
>   data <- dlapply(function(d, p) p$adjust_position(d, scales, "after"))
>   scales <- scales$minus(plot$scales$get_scales(c("x", "y", "z")))
>
>   legends(scales, FALSE)
>
> }
>
>
> library(ggplot2)
> data(mtcars)
>
> grid.newpage()
>
> hide_colour <- scale_colour_continuous()
> hide_colour$legend <- FALSE
>
> pushViewport(viewport(layout = grid.layout(2, 2)))
>
> p <- ggplot(data = mtcars) +
>   geom_point(mapping = aes(x = hp, y = mpg, colour = cyl)) +
>   hide_colour
>
> pushViewport(viewport(layout.pos.col = 1,
>                       layout.pos.row = 1))
>
> print(p, vp = current.viewport())
> upViewport()
>
> p <- ggplot(data = mtcars) +
>   geom_point(mapping = aes(x = drat, y = disp, colour = cyl)) +
>   hide_colour
>
>
> pushViewport(viewport(layout.pos.col = 2,
>                       layout.pos.row = 1))
>
> print(p, vp = current.viewport())
> upViewport()
>
> p <- ggplot(data = mtcars) +
>   geom_point(mapping = aes(x = qsec, y = mpg, colour = cyl)) +
>   hide_colour
>
> pushViewport(viewport(layout.pos.col = 1,
>                       layout.pos.row = 2))
>
> print(p, vp = current.viewport())
> upViewport()
>
> pushViewport(viewport(layout.pos.col = 2,
>                       layout.pos.row = 2))
> grid.rect()
>
> p.legend <- get_legends(p)
> grid.draw(p.legend)
> ----------------------------------------------END CODE
>
>
>
>
> -----Original Message-----
> From: hadley wickham [mailto:h.wickham at gmail.com]
> Sent: Monday, September 10, 2007 7:58 AM
> To: Te, Kaom
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] ggplot legend consolidation
>
> > I have recently been introduced to the ggplot package by Hadley
> > Wickham and must say I am quite impressed so far at how easy it is to
> > make attractive plots, but one thing I am struggling over is how to
> > consolidate legends.
>
> It's not currently possible to consolidate them (although in the distant
> future that would be something nice to have), but you can turn them off:
>
> hide_colour <- scale_colour_continuous() hide_colour$legend <- FALSE
>
> p <- ggplot(data = mtcars) +
>   geom_point(mapping = aes(x = hp, y = mpg, colour = cyl)) +
>   hide_colour
>
> You'll also need to twiddle your viewports a little so that you still
> have space for the viewport, since space will not be allocated
> automatically anymore.
>
> The next thing is to extract the grob for the legend itself - this is a
> little tricker, because there's currently no way to get at the scales
> after they have been "trained" with the data.  Load get_legends from
> http://pastie.textmate.org/95755, and then you can do:
>
> grid.newpage(); grid.draw(get_legends(p))
>
> If you're not familiar enough with grid to stitch all of these pieces
> together, please let me know, but this should be enough to get you
> started.
>
> Hadley
>


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