Reverse order of x axis labels on grouped bar chart after coord_flip()

Question

In the plot shown below I am trying to change the order of the labels on the y axis (x axis before coord_flip()). I would like 1 to be on top and 16 at the bottom.

levels <- c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)

library(ggplot2)
ggplot(all_Q, aes(x=qid, y=correct_per, fill=group), group=qid) + 
  geom_bar(stat="identity", position=position_dodge()) + 
  scale_x_discrete(name = "Questions", limits = levels) + 
  scale_y_continuous(name = "Percent correct") + 
  coord_flip()

Here is what I have tried to so far:

levels <- c(16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1) -> No change.

limits = rev(levels) -> no change

limits = rev(levels(levels)) -> suggestion from this question/answer img below

Reproducible example with a subset of the questions (8,9,10,11)

dput() output:

structure(list(group = structure(c(1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L), .Label = c("A", "B", "C", "D"), class = "factor"), correct_per = c(90.4761904761905, 100, 100, 87.5, 83.3333333333333, 90.9090909090909, 84.6153846153846, 87.5, 80.9523809523809, 88.6363636363636, 100, 70.8333333333333, 63.4146341463415, 76.7441860465116, 76.9230769230769, 62.5), nr_correct = c(38L, 44L, 26L, 21L, 35L, 40L, 22L, 21L, 34L, 39L, 26L, 17L, 26L, 33L, 20L, 15L), nr_incorrect = c(4L, 0L, 0L, 3L, 7L, 4L, 4L, 3L, 8L, 5L, 0L, 7L, 15L, 10L, 6L, 9L), length = c(42L, 44L, 26L, 24L, 42L, 44L, 26L, 24L, 42L, 44L, 26L, 24L, 41L, 43L, 26L, 24L), qid = c("8", "8", "8", "8", "9", "9", "9", "9", "10", "10", "10", "10", "11", "11", "11", "11")), .Names = c("group", "correct_per", "nr_correct", "nr_incorrect", "length", "qid"), row.names = c(NA, -16L), class = c("tbl_df", "tbl", "data.frame"))

save to file 

all_Q <- dget(filename)

levels <- c(8,9,10,11)

    ggplot(all_Q, aes(x=qid, y=correct_per, fill=group), group=qid) + 
      geom_bar(stat="identity", position=position_dodge()) + 
      scale_x_discrete(name = "Questions", limits = levels) + 
      scale_y_continuous(name = "Percent correct") + 
      coord_flip()

Please show a small reproducible example with `dput` – akrun Mar 23 '18 at 09:56 — akrun, Mar 23 '18 at 09:56

jay.sf · Answer 1 · 2018-03-23T22:38:33.467

It's best to work with factors in specific order. I'm sure what you want is

all_Q$qid <- factor(all_Q$qid, levels = c(11, 10, 9, 8))

ggplot(all_Q, aes(x=qid, y=correct_per, fill=group), group=qid) + 
  geom_bar(stat="identity", position=position_dodge()) + 
  scale_x_discrete(name = "Questions") +
  scale_y_continuous(name = "Percent correct") + 
  coord_flip()

Yields:

Compare:

all_Q$qid <- factor(all_Q$qid, levels = c(11, 10, 9, 8))

Yields:

score 1 · Accepted Answer · answered Mar 23 '18 at 10:37

Column all_Q$qid is factor, thus you can specify limits (order) passing non-numeric vector.

library(ggplot2)
# Don't use group as you're already grouping by fill
ggplot(all_Q, aes(qid, correct_per, fill = group)) + 
    geom_bar(stat = "identity", position = "dodge") + 
    # Passing character vector from 16 to 1 
    scale_x_discrete(limits = as.character(16:1)) + 
    # Don't use function scale_y_* only for naming
    # With function labs you can specify all the names
    labs(x = "Questions",
         y = "Correct, %",
         fill = "My fill") +
    coord_flip()

Reverse order of x axis labels on grouped bar chart after coord_flip()

2 Answers2