How to sensibly align two legends when using cowplot in R?-CodePudding

A similar question was asked

As you can see, the two legends have quite a bit of vertical space between them and they are not centred with the plot.

Is there a way to align the two legends so they look something like this:

I'm not sure if it is possible using cowplot... or is there a way to maybe use ggplot's annotate to place the legends?

CodePudding user response：

I would probably go for patchwork, as Stefan suggests, but within cowplot you probably need to adjust the legend margins:

theme_margin <- theme(legend.box.margin = margin(100, 10, 100, 10))
legend  <- cowplot::get_legend(allPlots[[1]]   theme_margin)
legend1 <- cowplot::get_legend(newPlot   theme_margin)
combineLegend <- cowplot::plot_grid(
  legend,
  legend1,
  nrow = 2)

# now make plot
cowplot::plot_grid(plotGrid, 
                   combineLegend, 
                   rel_widths = c(0.9, 0.11),
                   ncol = 2)

CodePudding user response：

If switching to another package is an option for you I would suggest to use patchwork to glue your plots together. One feature offered by patchwork is that using plot_spacer you could easily add some empty panels above and below your legends to "move" them to the center and thereby getting rid of the empty space. Depending on your final result or the height of your final plot you probably have to play a bit around with the heights and/or widths arguments:

library(cowplot)
library(ggplot2)
library(patchwork)

set.seed(123)

# create some data
dat <- NULL
for (i in 1:20) {
  x <- LETTERS[1:5]
  y <- paste0("var", seq(1, 5))
  dat[[i]] <- expand.grid(X = x, Y = y)
  dat[[i]]$Z <- runif(25, 0, 1)
}

# plotting function
plotFun <- function(data) {
  ggplot(data, aes(X, Y, fill = Z))  
    geom_tile()  
    theme(
      aspect.ratio = 1,
      legend.justification = c(0, 1),
      axis.text.x = element_blank(),
      axis.ticks.x = element_blank(),
      axis.text.y = element_blank(),
      axis.ticks.y = element_blank()
    )  
    labs(x = NULL, y = NULL)
}

# set up to plot on a grid
allPlots <- lapply(dat, plotFun)
allPlotsAlter <- lapply(allPlots, function(x) x   theme(legend.position = "none"))
n <- length(allPlotsAlter)
nRow <- floor(sqrt(n))
plotGrid <- wrap_plots(grobs = allPlotsAlter, nrow = nRow)

# create a different type of legend
newPlot <- ggplot(iris, aes(x = Sepal.Length, y = Petal.Length, fill = Species))  
  geom_bar(stat = "identity")  
  theme(legend.justification = c(0, 1))

# get both legends and combine
legend <- cowplot::get_legend(allPlots[[1]])
legend1 <- cowplot::get_legend(newPlot)

combineLegend <- plot_spacer()   legend   legend1   plot_spacer()   plot_layout(ncol = 1, heights = c(.5, 1, 1, .5))

wrap_elements(plotGrid)   combineLegend   plot_layout(widths = c(4, 1))