Ggplot2: add distribution jitter next to the legend panel

Question

Non-trivial ggplot task

I compare the spatial distribution of a variable at two points using maps with a fixed color scale - to display the actual change. It would be nice to add the distribution of variables near the legend bars as jitter points.

The desired plot should look something like this: the supposed red jitter points are added manually (I just used paint.net) to the plot created by R

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Play cards

To play maps, an R object named fortIT . This is a hardened (using ggplot2::fortify ) SpatialPolygonsDataFrame from the Italian NUTS-2 regions with data attached. RData strong> file can be downloaded here [89KB]

And the code for the cards:

 require(dplyr) require(ggplot2) require(ggthemes) require(gridExtra) require(rgeos) require(maptools) require(cowplot) require(viridis) # load the data load(url("https://ikashnitsky.imtqy.com/misc/160227-SO-question/fortIT.RData")) # produce the first map gIT1 <- ggplot()+ geom_polygon(data = fortIT, aes(x=long, y=lat, group=group, fill=tsr03), color='grey30',size=.1)+ scale_fill_viridis('TSR\n2003',limits=range(fortIT[,9:10]))+ # !!! limits fix the color scale coord_equal(xlim=c(4000000, 5500000), ylim=c(1500000,3000000))+ guides(fill = guide_colorbar(barwidth = 1.5, barheight = 15))+ theme_map()+ theme(panel.border=element_rect(color = 'black',size=.5,fill = NA), legend.position = c(1, 1), legend.justification = c(1, 1), legend.background = element_rect(colour = NA, fill = NA), legend.title = element_text(size=15), legend.text = element_text(size=15))+ scale_x_continuous(expand=c(0,0)) + scale_y_continuous(expand=c(0,0)) + labs(x = NULL, y = NULL) # produce the second map gIT2 <- ggplot()+ geom_polygon(data = fortIT, aes(x=long, y=lat, group=group, fill=tsr43), color='grey30',size=.1)+ scale_fill_viridis('TSR\n2043',limits=range(fortIT[,9:10]))+ coord_equal(xlim=c(4000000, 5500000), ylim=c(1500000,3000000))+ guides(fill = guide_colorbar(barwidth = 1.5, barheight = 15))+ theme_map()+ theme(panel.border=element_rect(color = 'black',size=.5,fill = NA), legend.position = c(1, 1), legend.justification = c(1, 1), legend.background = element_rect(colour = NA, fill = NA), legend.title = element_text(size=15), legend.text = element_text(size=15))+ scale_x_continuous(expand=c(0,0)) + scale_y_continuous(expand=c(0,0)) + labs(x = NULL, y = NULL) # align both maps side by side gIT <- plot_grid(gIT1,gIT2,ncol=2,labels=LETTERS[1:2],label_size=20) ggsave('italy.png',gIT,width=12,height=7,dpi=192) 

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Additional Information

The variables displayed on the maps are indicators of total support in 2003 (panel A) and 2043 (panel B, Eurostat regional projection). The ratio of total support is the ratio of the working-age population (15-64) to the number of non-working age (under 15 and over 65).

Answer 1

Whenever an ordinary legend is required, I find it preferable to draw the legend as a separate story, and then combine it.

For example, we can define the following function:

 plot_legend <- function(dots, limits, title, bins = 20) { n <- 100 tiles <- data.frame(x = rep(0.5, n), y = seq(limits[1], limits[2], length.out = n)) ggplot() + geom_raster(data=tiles, aes(x = x, y = y, fill = y), interpolate = TRUE) + geom_dotplot(data = data.frame(x = dots), aes(x = -.05, y = x, fill = ..y..), stackdir = "down", binaxis = "y", binwidth = diff(limits)/bins, dotsize = .8) + scale_x_continuous(limits = c(-5, 1), expand = c(0, 0)) + scale_y_continuous(expand = c(0, 0), position = "right") + ggtitle(title) + theme_cowplot(12) + theme(axis.text.x = element_blank(), axis.ticks.x = element_blank(), axis.line = element_blank(), axis.title = element_blank(), plot.title = element_text(face = "plain", hjust = 1), legend.position = "none") } 

What we can use like this:

 require(ggplot2) require(cowplot) require(viridis) dots <- 3*runif(100) range <- c(0, 3) plot_legend(dots, range, "random numbers") + scale_fill_viridis() 

Now we use this together with the card code. This requires a bit of tinkering with the final placement of legends in the drawings, but it is not too difficult.

 require(dplyr) load(url("https://ikashnitsky.imtqy.com/misc/160227-SO-question/fortIT.RData")) # extract tsr03 and tsr43 data fortIT %>% group_by(group) %>% summarize(tsr03 = tsr03[1], tsr43 = tsr43[1]) -> df_tsr # get color range limits limits <- range(fortIT[,9:10]) # make the legends legIT1 <- plot_legend(df_tsr$tsr03, limits, "TSR 2003") + scale_fill_viridis() legIT2 <- plot_legend(df_tsr$tsr43, limits, "TSR 2043") + scale_fill_viridis() # produce the first map gIT1 <- ggplot()+ geom_polygon(data = fortIT, aes(x=long, y=lat, group=group, fill=tsr03), color='grey30', size=.1) + scale_x_continuous(expand=c(0,0)) + scale_y_continuous(expand=c(0,0)) + scale_fill_viridis('TSR\n2003', limits = limits, guide = "none") + coord_equal(xlim=c(4000000, 5500000), ylim=c(1500000, 3000000)) + theme_map() + theme(panel.border=element_rect(color = 'black',size=.5,fill = NA)) # produce the second map gIT2 <- ggplot()+ geom_polygon(data = fortIT, aes(x=long, y=lat, group=group, fill=tsr43), color='grey30',size=.1)+ scale_x_continuous(expand=c(0,0)) + scale_y_continuous(expand=c(0,0)) + scale_fill_viridis('TSR\n2043', limits = limits, guide = "none") + coord_equal(xlim=c(4000000, 5500000), ylim=c(1500000, 3000000)) + theme_map() + theme(panel.border=element_rect(color = 'black',size=.5,fill = NA)) # put everything together plot_grid(ggdraw(gIT1) + draw_plot(legIT1, .62, .35, .35, .55), ggdraw(gIT2) + draw_plot(legIT2, .62, .35, .35, .55), ncol=2, labels="AUTO") 

Two comments:

• The size of the summed points can be controlled by the bins argument of the plot_legend() function. The more bins , the less points.

• I usually deleted the borders around each map, but I tried here to reproduce the original shape as close as possible.

Answer 2

you can replace the legend with those who have a story panel attached to it with density information,

 g <- ggplotGrob(p) leg = gtable_filter(g, "guide-box") dd <- ddply(fortIT, "group", summarise, fill=unique(tsr03)) dum <- ggplot(dd, aes(0,y=fill)) + geom_dotplot(fill="red", binaxis = "y", dotsize=0.5, stackdir = "down")+ scale_y_continuous(lim=range(fortIT[,c("tsr03", "tsr43")]), expand=c(0,0)) + theme_void() dummy_panel <- gtable_filter(ggplotGrob(dum), "panel") dummy_panel$layout$clip <- FALSE a <- leg[[1]][[1]][[1]][[1]] a <- gtable_add_cols(a, unit(1,"cm"), 0) a <- gtable_add_grob(a, dummy_panel, 4, 1) a$layout$clip <- FALSE grid.newpage() grid.draw(a) leg[[1]][[1]][[1]][[1]] <- a g$grobs[g$layout$name=="guide-box"] <- list(leg) library(grid) grid.newpage() grid.draw(g)