Adding line with specific df value to each bar in ggplot - r

Question

My df is organized this way for example:
OCCURED_COUNTRY_DESC | a | b | c | d | flagged | type | MedDRA_PT| **E** |
__________________________________________________________________________
UNITED STATES |403|1243|473|4077| yes | disp | Seizure |144.208|
__________________________________________________________________________
My data:
structure(list(OCCURED_COUNTRY_DESC = c("AUSTRALIA", "AUSTRIA",
"BELGIUM", "BRAZIL", "CANADA"), a = c(4L, 7L, 20L, 5L, 11L),
b = c(31, 27, 100, 51, 125), c = c(872, 869, 856, 871, 865
), d = c(5289, 5293, 5220, 5269, 5195), w = c(876, 876, 876,
876, 876), x = c(5320, 5320, 5320, 5320, 5320), y = c(35L,
34L, 120L, 56L, 136L), z = c(6161, 6162, 6076, 6140, 6060
), N = c(6196, 6196, 6196, 6196, 6196), k = c("0.5", "0.5",
"0.5", "0.5", "0.5"), SOR = c(0.80199821407511, 1.52042360060514,
1.21312776329214, 0.615857869962066, 0.539569644832803),
log = c(-0.318329070860348, 0.604473324558599, 0.278731499148795,
-0.699330656240263, -0.890118907611227), LL99 = c(-0.695969674426877,
0.382102954188229, 0.198127619344382, -1.00534117464748,
-1.03425468471322), UL99 = c(-0.0544058884186467, 0.763880731966007,
0.337239065783058, -0.482651467660248, -0.785935460582379
), flagged = c("no", "no", "no", "no", "yes"), type = c(NA,
NA, NA, NA, "under"), MedDRA_PT = c("Seizure", "Seizure",
"Seizure", "Seizure", "Seizure"), E = c(5.11098506333901,
4.43283582089552, 16.3984674329502, 8.43063199848168, 20.8132820019249
)), row.names = c(NA, -5L), class = c("tbl_df", "tbl", "data.frame"
))
I am using ggplot2 to create a bar chart using the following piece of code:
test2 %>% #using test2 as the df
ggplot(aes(a, OCCURED_COUNTRY_DESC, fill=type)) +
geom_bar(stat="identity")+
scale_fill_manual(values = c("disp" = "#FF8C00",
"under" = "#7EC0EE",
"NA"="#EEE9E9"))+
theme_classic()+
labs(title = "Seizure",
x = "Count",
y = "")
What I would like to do is to add a black line in each bar correspondent to the E value, from the dataframe, for that country. However I haven't been successful. Can someone kindly guide me on how to achieve this?
Thanks!

Answer 1

One option to achieve your desired result would be via a geom_segment, where you map your E column on both the x and the xend position. "Tricky" part are the y positions. However, as a categorical axis is still a numeric axis we could add a helper column to your data which contains the numeric positions of your categorical OCCURED_COUNTRY_DESC column. This helper column could then be mapped on the y and the yend aes needed by geom_segment where we also take into account the width of the bars:
library(ggplot2)
test2$OCCURED_COUNTRY_DESC_num <- as.numeric(factor(test2$OCCURED_COUNTRY_DESC))
width <- .9 # defautlt width of bars
ggplot(test2, aes(a, OCCURED_COUNTRY_DESC, fill = type)) +
geom_bar(stat = "identity") +
geom_segment(aes(x = E, xend = E,
y = OCCURED_COUNTRY_DESC_num - width / 2,
yend = OCCURED_COUNTRY_DESC_num + width / 2),
color = "black", size = 1) +
scale_fill_manual(values = c(
"disp" = "#FF8C00",
"under" = "#7EC0EE",
"NA" = "#EEE9E9"
)) +
theme_classic() +
labs(
title = "Seizure",
x = "Count",
y = ""
)