Plot grouped barplot with absolute and percent values + labels - r

Question

I am quite new to R and especially to ggplot. For my next result I think I have to change from plot() to ggplot() where I need your help:
I have a dataframe with numeric values. One column is an absolute number, the other one is the belonging percentage value. I have 3 of this "two groups" indicators a, b and c.
The rownames are the 6 observations and are stored in the first column "X".
I want to plot them in a kind of grouped barplot, where the absolute+percent column is next to each other for the 3 indicators.
Sample dataframe:
df = data.frame(X = c("e 1","e 1,5","e 2","e 2,5","e 3","e 3,5","e 4"),
a_abs=c(-0.3693,-0.0735,-0.019,0.0015,0,-0.0224,-0.0135),
a_per=c(-0.4736,-0.0943,-0.0244,0.0019,0,-0.0287,-0.0173),
b_abs=c(-0.384,-0.0733,-0.0173,0.0034,0,-0.0204,-0.0179),
b_per=c(-0.546,-0.1042,-0.0246,0.0048,0,-0.029,-0.0255),
c_abs=c(-0.3876,-0.0738,-0.019,0.0015,0,-0.0225,-0.0137),
c_per=c(-0.4971,-0.0946,-0.0244,0.0019,0,-0.0289,-0.0176))
Thanks to #jonspring i got the following plot by using this code:
df3 <- df %>%
gather(column, value, -X) %>%
mutate(group = str_sub(column, end = 2),
stat = str_sub(column, start = 4)) %>%
select(-column) %>%
spread(stat, value) %>%
mutate(combo_label = paste(sep="\n",
scales::comma(abs, accuracy = 0.001),
scales::percent(per, accuracy = 0.01)))
df3$group = gsub(df3$group,pattern = "CK",replacement = "Cohen's\nKappa")
df3$group = gsub(df3$group,pattern = "JA",replacement = "Jaccard")
df3$group = gsub(df3$group,pattern = "KA",replacement = "Krippen-\ndorff's Alpha")
crg = ifelse(df3$abs< 0,"red","darkgreen")
ggplot(df3, aes(group, abs, label = combo_label)) +
geom_segment(aes(xend = group,
yend = 0),
color = crg) +
geom_point() +
geom_text(vjust = 1.5,
size = 3,
lineheight = 1.2) +
scale_y_continuous(expand = c(0.2,0)) +
facet_grid(~X) +
labs(x= "Exponent", y = "Wert")
plot output
When i zoom and have the positive values visible, the labels are written inside the segments. How to place them above / below depending of a positive or negative value?
Zoom with coord_cartesian(ylim = c(-0.015,0.005))
zoomed plot
Thank you for your helping hands.
EDIT: I found the solution already. Like the color changement from red to green i used ifelse for the vjust parameter.

Answer 1

There are a lot of varieties of ways to display this sort of data with ggplot. I highly recommend you check out https://r4ds.had.co.nz/data-visualisation.html if you haven't already.
One suggestion you'll find there is that ggplot almost always works better if you first convert your data into long (aka "tidy") form. This puts each of the dimensions of the data into its own column, so that you can map the dimension to a visual aesthetic. Here's one way to do that:
library(tidyverse)
df2 <- df %>%
gather(column, value, -X) %>%
mutate(group = str_sub(column, end = 1),
stat = str_sub(column, start = 3),
value_label = if_else(stat == "per",
scales::percent(value, accuracy = 0.1),
scales::comma(value, accuracy = 0.01)))
Now, the group a/b/c is in its own column, as is the type of data abs/per, the values are all together in one column, and we also have text labels that suit the type of data.
> head(df2)
X column value group stat value_label
1 e 1 a_abs -0.3693 a abs -0.37
2 e 1,5 a_abs -0.0735 a abs -0.07
3 e 2 a_abs -0.0190 a abs -0.02
4 e 2,5 a_abs 0.0015 a abs 0.00
5 e 3 a_abs 0.0000 a abs 0.00
6 e 3,5 a_abs -0.0224 a abs -0.02
With that out of the way, it's simpler to try out different combinations of ggplot options, which can help highlight different comparisons within the data.
For instance, if you want to compare the different observations within each group, you could put each group into a facet, and each observation along the x axis:
ggplot(df2, aes(X, value, label = value_label)) +
geom_segment(aes(xend = X, yend = 0), color = "blue") +
geom_point() +
geom_text(vjust = 2, size = 2) +
facet_grid(stat~group)
Or if you want to highlight how the different groups compared within each observation, you could swap them, like this:
ggplot(df2, aes(group, value, label = value_label)) +
geom_segment(aes(xend = group, yend = 0), color = "blue") +
geom_point() +
geom_text(vjust = 2, size = 2) +
facet_grid(stat~X)
You might also try combining the abs and per data, since they only vary slightly based on the different denominators applicable to each group and/or observation. To do that, it might be simpler to transform the data to keep each abs and per together:
df3 <- df %>%
gather(column, value, -X) %>%
mutate(group = str_sub(column, end = 1),
stat = str_sub(column, start = 3)) %>%
select(-column) %>%
spread(stat, value) %>%
mutate(combo_label = paste(sep="\n",
scales::comma(abs, accuracy = 0.01),
scales::percent(per, accuracy = 0.1)))
ggplot(df3, aes(group, abs, label = combo_label)) +
geom_segment(aes(xend = group, yend = 0), color = "blue") +
geom_point() +
geom_text(vjust = 1.5, size = 2, lineheight = 0.8) +
scale_y_continuous(expand = c(0.2,0)) +
facet_grid(~X)