Pie Charts in ggsubplot (ggplot2)

Question

Another interesting ggplot2 challenge! I'm trying to create a ggsubplot call that gives pie charts over a world map. The tough thing seems to be that pie charts in ggplot2 are stacked bar charts with polar coordinates, and that addition of coord_polar affects not just the subplot geom but the whole map itself. Does anyone know how to apply a certain coordinate scheme only to only one part of the subplot call? This is what I have so far:

library(ggplot2)
library(maps)
library(mapproj)
#install.packages("devtools")
library(devtools)
# install ggsubplot from github repo, not currently on CRAN
install_github(username="garrettgman", repo="ggsubplot")

world = map_data("world")

loc_pie = structure(list(Region = structure(c(3L, 5L, 7L, 8L, 9L, 10L, 
11L, 12L, 13L, 15L, 16L, 2L, 14L, 2L, 4L, 5L, 6L, 7L, 9L, 10L
), .Label = c("", "ANT/SO", "ARC", "EPR/GAL", "GOM/CAR", "IND", 
"MAR", "MED", "N-ATL", "NE-ATL", "NE-PAC", "NW-ATL", "NW-PAC", 
"SE-ATL", "SE-PAC", "SW-ATL", "SW-PAC"), class = "factor"), Group3 = structure(c(1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L), .Label = c("Annelida", "Choanoflagellata", "Chordata", 
"Cnidaria", "Crustacea", "Echinodermata", "Foraminifera", "Mollusca", 
"Nematoda", "Other", "Platyhelminthes", "Porifera"), class = "factor"), 
ones = c(1, 1, 5, 1, 1, 1, 18, 3, 1, 4, 8, 1, 1, 2, 1, 1, 
6, 1, 2, 5), tot = c(5, 30, 11, 16, 28, 22, 51, 25, 78, 13, 
32, 57, 61, 57, 15, 30, 20, 11, 28, 22), div = c(0.2, 0.0333333333333333, 
0.454545454545455, 0.0625, 0.0357142857142857, 0.0454545454545455, 
0.352941176470588, 0.12, 0.0128205128205128, 0.307692307692308, 
0.25, 0.0175438596491228, 0.0163934426229508, 0.0350877192982456, 
0.0666666666666667, 0.0333333333333333, 0.3, 0.0909090909090909, 
0.0714285714285714, 0.227272727272727), lat = c(71.4493167, 
19.9897167, 23.5874333, 37.6802167, 55.13365, 36.6889333, 
35.9565333, 35.53935, 30.4266, -30.32195, -33.2038, -65.8756333, 
-17.12415, -65.8756333, 0.1135, 19.9897167, -14.5800667, 
23.5874333, 55.13365, 36.6889333), long = c(-1.0550667, -81.3430667, 
-41.2278667, 15.9298833, -30.4984333, -17.4906167, -149.4363333, 
-63.01795, 156.3570833, -110.23255, -31.20155, -25.4557, 
0.0881833, -25.4557, -101.07455, -81.3430667, 77.4312667, 
-41.2278667, -30.4984333, -17.4906167)), .Names = c("Region", 
"Group3", "ones", "tot", "div", "lat", "long"), row.names = c(NA, 
20L), class = "data.frame")

ggplot(data=loc_pie) + geom_polygon(data=world, aes(x=long, y=lat, group =group),colour="grey40", fill="grey40") + geom_subplot(height=12, aes(long, lat, group=Region, subplot = (geom_bar(aes(x = factor(1),   y=div, fill=factor(Group3)), width =1, height = 2,stat="identity"))))

Doesn't look like I can post images because I'm a new user.

![world map with stacked bar chart subplots][1]

Any ideas on how to incorporate the polar coordinates for only the subplot? Thanks so much.

Answer 1

Here is a solution with the latest version of ggplot2 and ggtree:

library(maps)
library(mapproj)
library(ggplot2)
library(ggtree)
library(dplyr)
library(magrittr)

world = map_data("world")

p <- ggplot(data=world, aes(x=long, y=lat, group =group)) + geom_polygon(colour="grey40", fill="grey40")

for (name in unique(loc_pie[['Region']])) {
  loc_region <- filter(loc_pie, Region %in% name)
  pie_tmp <- ggplot(data = loc_region, aes(x = factor(1), y = div, fill = Group3)) +
    geom_bar(width = 1, stat = "identity") + coord_polar(theta = "y") +
    scale_fill_discrete(drop = FALSE) +
    xlab(NULL) + ylab(NULL) + theme_tree() +
    theme_transparent()
  lat_region <- loc_region[[1,'lat']]
  long_region <- loc_region[[1,'long']]
  p %<>% subview(pie_tmp, long_region, lat_region, width = .07, height = .07)
}

p

The width ang height have been picked manually, they correspond to the proportion of the subview with respect to the full one.

For sake of completness, loc_pie can be obtained by:

loc_pie = structure(
  list(
    Region = structure(
      c(
        3L,
        5L,
        7L,
        8L,
        9L,
        10L,
        11L,
        12L,
        13L,
        15L,
        16L,
        2L,
        14L,
        2L,
        4L,
        5L,
        6L,
        7L,
        9L,
        10L
      ),
      .Label = c(
        "",
        "ANT/SO",
        "ARC",
        "EPR/GAL",
        "GOM/CAR",
        "IND",
        "MAR",
        "MED",
        "N-ATL",
        "NE-ATL",
        "NE-PAC",
        "NW-ATL",
        "NW-PAC",
        "SE-ATL",
        "SE-PAC",
        "SW-ATL",
        "SW-PAC"
      ),
      class = "factor"
    ),
    Group3 = structure(
      c(
        1L,
        1L,
        1L,
        1L,
        1L,
        1L,
        1L,
        1L,
        1L,
        1L,
        1L,
        2L,
        2L,
        3L,
        3L,
        3L,
        3L,
        3L,
        3L,
        3L
      ),
      .Label = c(
        "Annelida",
        "Choanoflagellata",
        "Chordata",
        "Cnidaria",
        "Crustacea",
        "Echinodermata",
        "Foraminifera",
        "Mollusca",
        "Nematoda",
        "Other",
        "Platyhelminthes",
        "Porifera"
      ),
      class = "factor"
    ),
    ones = c(1, 1, 5, 1, 1, 1, 18, 3, 1, 4, 8, 1, 1, 2, 1, 1,
             6, 1, 2, 5),
    tot = c(5, 30, 11, 16, 28, 22, 51, 25, 78, 13,
            32, 57, 61, 57, 15, 30, 20, 11, 28, 22),
    div = c(
      0.2,
      0.0333333333333333,
      0.454545454545455,
      0.0625,
      0.0357142857142857,
      0.0454545454545455,
      0.352941176470588,
      0.12,
      0.0128205128205128,
      0.307692307692308,
      0.25,
      0.0175438596491228,
      0.0163934426229508,
      0.0350877192982456,
      0.0666666666666667,
      0.0333333333333333,
      0.3,
      0.0909090909090909,
      0.0714285714285714,
      0.227272727272727
    ),
    lat = c(
      71.4493167,
      19.9897167,
      23.5874333,
      37.6802167,
      55.13365,
      36.6889333,
      35.9565333,
      35.53935,
      30.4266,
      -30.32195,
      -33.2038,
      -65.8756333,-17.12415,
      -65.8756333,
      0.1135,
      19.9897167,
      -14.5800667,
      23.5874333,
      55.13365,
      36.6889333
    ),
    long = c(
      -1.0550667,
      -81.3430667,-41.2278667,
      15.9298833,
      -30.4984333,
      -17.4906167,
      -149.4363333,-63.01795,
      156.3570833,
      -110.23255,
      -31.20155,
      -25.4557,
      0.0881833,
      -25.4557,
      -101.07455,
      -81.3430667,
      77.4312667,-41.2278667,
      -30.4984333,
      -17.4906167
    )
  ),
  .Names = c("Region",
             "Group3", "ones", "tot", "div", "lat", "long"),
  row.names = c(NA,
                20L),
  class = "data.frame"
)