CODEWITHSUNDEEP
rggplot2
Mario
Mario

Reputation: 63

Connect points within one item but across groups with arrows

My chart currently consists of multiple x-axis items that get 2 y-axis values each (one per group, means using stat_summary). However, the chart is flipped for the sake of stat_summary's mean function (but that is not the point here).

df <- data.frame(
  value = c(0, 0, -2, 1, 2, -2, 3, 1, 2, 3, 2, -1),
  type = c('P', 'P', 'E', 'P', 'E', 'E', 'P', 'E', 'E', 'E', 'P', 'P'),
  item = c('well-written', 'concise', 'well-written', 'clear', 'concise', 'clear', 'lively', 'fair', 'lively', 'pleasing', 'pleasing', 'fair')
)

ggplot(df, aes(x=item, y=value, colour=type)) +
  stat_summary(fun.y=mean, geom='point', size=3) + 
  scale_y_continuous(limits=c(-3, 3), breaks=c(-3, -2, -1, 1, 2, 3), minor_breaks=c(0)) +
  scale_linetype_discrete() +
  coord_flip()

See my current plot, without any arrows (status quo): enter image description here

What I want is, for every single item ("well-written", "concise", ...) to draw an arrow from E (the red point) to P (the blue point). Hence, I want multiple horizontal arrows, one for each item.

How?

Just one little addition here: I know that I would not need the mean function in this example but my actual data is much larger and contains multiple P/well-written, E/concise, etc. values so that the mean function makes sense

Upvotes: 4

Views: 1444

Answers (1)

erc
erc

Reputation: 10133

Here's an approach, which however requires a second data frame to be created first:

library(tidyr)
df2 <- df %>% spread(type, value)

Then you can add geom_segment like so:

ggplot(df, aes(x=item, y=value, colour=type)) +
  stat_summary(fun.y=mean, geom='point', size=3) + 
  scale_y_continuous(limits=c(-3, 3), breaks=c(-3, -2, -1, 1, 2, 3), minor_breaks=c(0)) +
  scale_linetype_discrete() +
  coord_flip() +
  geom_segment(data = df2, aes(x = item, xend = item, y = E, yend = P, group = item), 
               colour = "black", 
               arrow = arrow())

enter image description here

Upvotes: 2

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