Two legends for polar ggplot (with one customized)

Question

Here is my data:

data <- structure(list(Indicator = structure(c(1L, 1L, 1L, 2L, 2L, 2L, 
3L, 3L, 3L, 6L, 6L, 6L, 6L, 4L, 4L, 5L, 5L, 1L, 1L, 1L, 2L, 2L, 
2L, 3L, 3L, 3L, 6L, 6L, 6L, 6L, 4L, 4L, 5L, 5L, 1L, 1L, 1L, 2L, 
2L, 2L, 3L, 3L, 3L, 6L, 6L, 6L, 6L, 4L, 4L, 5L, 5L, 1L, 1L, 1L, 
2L, 2L, 2L, 3L, 3L, 3L, 6L, 6L, 6L, 6L, 4L, 4L, 5L, 5L, 1L, 1L, 
1L, 2L, 2L, 2L, 3L, 3L, 3L, 6L, 6L, 6L, 6L, 4L, 4L, 5L, 5L), .Label = c("Causality", 
"Climatechangeriskperceptions", "Currentadaptationoptions", "Fishingasalivelihoodactivity", 
"Governance", "Roleofshadowstateactors"), class = "factor"), 
    Village = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
    1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
    2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 
    3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 4L, 4L, 
    4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 5L, 
    5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 
    5L), .Label = c("Andra", "lahapau", "Pelipowai", "Ponam", 
    "Tulu"), class = "factor"), Variables = structure(c(13L, 
    3L, 10L, 11L, 12L, 16L, 5L, 8L, 1L, 2L, 15L, 17L, 6L, 14L, 
    9L, 4L, 7L, 13L, 3L, 10L, 11L, 12L, 16L, 5L, 8L, 1L, 2L, 
    15L, 17L, 6L, 14L, 9L, 4L, 7L, 13L, 3L, 10L, 11L, 12L, 16L, 
    5L, 8L, 1L, 2L, 15L, 17L, 6L, 14L, 9L, 4L, 7L, 13L, 3L, 10L, 
    11L, 12L, 16L, 5L, 8L, 1L, 2L, 15L, 17L, 6L, 14L, 9L, 4L, 
    7L, 13L, 3L, 10L, 11L, 12L, 16L, 5L, 8L, 1L, 2L, 15L, 17L, 
    6L, 14L, 9L, 4L, 7L), .Label = c("alternativelivelihood", 
    "anyactorsinvolvedinsustainability", "Attributionfactors", 
    "discusswithelectedleaders", "Effortsdirectedtoreducerisks", 
    "fishercommunityinfluence", "Infrastructureeffectiveness", 
    "multiplicityofactors", "Occupationforchildren", "Reversibility", 
    "Riskasamajorconsideration", "Riskbeingaddressed", "Statusoffisheries", 
    "Timefishing", "Whatwasdone", "Whoisatrisk", "whowasinvolved?"
    ), class = "factor"), legend.var = structure(c(1L, 2L, 3L, 
    4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L, 13L, 14L, 15L, 16L, 
    17L, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L, 13L, 
    14L, 15L, 16L, 17L, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 
    11L, 12L, 13L, 14L, 15L, 16L, 17L, 1L, 2L, 3L, 4L, 5L, 6L, 
    7L, 8L, 9L, 10L, 11L, 12L, 13L, 14L, 15L, 16L, 17L, 1L, 2L, 
    3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L, 13L, 14L, 15L, 
    16L, 17L), .Label = c("a", "b", "c", "d", "e", "f", "g", 
    "h", "i", "j", "k", "l", "m", "n", "o", "p", "q"), class = "factor"), 
    score = c(1, 0.97, 1, 0.76, 0.794, 1, 0.71, 0.9, 0.5, 1, 
    1, 1, 1, 0.49, 0.72, 1, 0.7, 1, 1, 0, 0.67, 0.5, 1, 0.2, 
    1, 1, 0.7, 0.4, 0.5, 0.3, 0.67, 0.5, 0.7, 0.8, 1, 0, 0.46, 
    0.56, 0.375, 1, 0.13, 0.3, 0.5, 0.3, 0.3, 0.4, 0.6, 1, 1, 
    0.7, 0.8, 1, 0.86, 0.69, 0.51, 0.429, 1, 0.44, 0.3, 0.5, 
    0.6, 0.6, 0.7, 0.8, 0.4, 0.79, 0.8, 1, 1, 0.82, 0.85, 0.25, 
    0.226, 1, 0.18, 0.1, 1, 0.7, 0.3, 0.6, 0.3, 0.48, 0.16, 0.4, 
    0.8)), .Names = c("Indicator", "Village", "Variables", "legend.var", 
"score"), class = "data.frame", row.names = c(NA, -85L))

I have made polar plots as follows:

library(ggplot2)
ggplot(data, aes(x = legend.var, y = score, fill = Indicator), color='black') + 
  geom_bar(width = 1, alpha=0.5, stat="identity") + 
  scale_y_continuous() + 
  coord_polar()  + 
  theme( axis.ticks = element_blank()) + 
  facet_wrap(~Village, nrow=2, ncol=3) + 
  guides(colour = guide_legend(title.hjust = 0.5))

As you can see in the data, column legend.var is grouped by the column indicator. I would like to insert a table or a second legend which associates each of the indicator with the legend.var and variables column. Ideally if this is inserted as a second legend, the unique items comprised in legend.var column would have the same fill color as the corresponding indicator. The fill legend is based on the column indicator. The inserted table/extra legend would comprise columns legend.var with a unique alphabet and column variables with the meaning of the respective alphabet. These can then have the same fill color as the corresponding indicator. I hope this is clear.

Answer 1

Here is a solution using a gtable:

library(ggplot2)
p <- ggplot(data, aes(x = legend.var, y = score, fill = Indicator), color='black') + 
  geom_bar(width = 1, alpha=0.5, stat="identity") + 
  scale_y_continuous() + 
  coord_polar()  + 
  theme( axis.ticks = element_blank()) + 
  facet_wrap(~Village, nrow=2, ncol=3) + 
  guides(colour = guide_legend(title.hjust = 0.5)) +
  theme(legend.position=c(0.85,0.25))

#create table
library(gridExtra)
tab <- tableGrob(unique(data[, c("legend.var", "Variables")]), 
                 show.rownames=FALSE, gpar.coretext=gpar(fontsize=10), 
                 gpar.coltext=gpar(fontsize=10, fontface='bold'),
                 gpar.corefill = gpar(fill = "grey90", col = "white"),
                 gpar.colfill = gpar(fill = "grey80", col = "white"))

#arrange grobs
library(gtable)
a <- gtable(unit(c(0.7, 0.3) ,c("npc")), unit(1, "npc"))
a <- gtable_add_grob(a, ggplotGrob(p),1,1)
a <- gtable_add_grob(a, tab,1,2)

#plot
grid.draw(a)

Answer 2

For a start, you may try something like this. You need to adjust arrangement and layout according to your own preferences.

library(ggplot2)
library(gridExtra)

gg <- ggplot(data, aes(x = legend.var, y = score, fill = Indicator), color='black') + 
  geom_bar(width = 1, alpha=0.5, stat="identity") + 
  coord_polar()  + 
  theme(axis.ticks = element_blank()) + 
  facet_wrap(~Village, nrow=2, ncol = 3) 

# create a table that translates legend.var to Variables 
tbl <- unique(data[ , c("legend.var", "Variables")])

# create a table grob 
tt <- tableGrob(d = tbl,
                col.just = "left",
                gpar.coretext = gpar(col = "black", cex = 0.5),
                gpar.coltext = gpar(col = "black", cex = 0.5, fontface = "bold"),
                gpar.rowtext = gpar(col = "black", cex = 0.5, fontface = "italic"))

# arrange plot and table grob
grid.arrange(gg, tt, ncol = 2)

update with a quick and dirty ggplot-only alternative

# create labels
labs <- with(tbl, paste(legend.var, Variables))

gg <- ggplot(data, aes(x = legend.var, y = score, fill = Indicator, col = Variables)) + 
  geom_bar(width = 1, alpha = 0.5, stat = "identity") +
  coord_polar()  + 
  theme(axis.ticks = element_blank()) + 
  facet_wrap(~ Village, nrow = 2, ncol = 3) +
  scale_color_grey(labels = labs, start = 0.8, end = 0.9)

gg