I want to make a bar chart (geom_bar) using ggplot2, where id is on the x-axis, and the value in N is on the y-axis. However, I want the x-axis to be ordered first by group and then in descending order of N.
id N group
1 1 A
2 2 A
3 1 A
4 5 A
5 2 A
6 3 B
7 15 B
8 4 B
9 15 C
10 1 C
The id column levels would be:
Levels: 4, 2, 5, 3, 1, 7, 8, 6, 9, 10
I was able to reorder the data table in the desired order (except N is ascending) with the following; however, it does not alter the levels of id, which seems to be needed to change the order id is plotted on the x-axis:
dt <- dt[with(dt, order(group, factor(N, order(group)))), ]
Below is a representation of the order I'm looking for.
id N group
4 5 A
2 2 A
5 2 A
3 1 A
1 1 A
7 15 B
8 4 B
6 3 B
9 15 C
10 1 C
The key is to arrange the level of the 'id' column.
id <- 1:10
N <- c(1,2,1,5,2,3,15,4,15,1)
group <- c(rep("A", 5), rep("B", 3), rep("C", 2))
df <- data.frame(id, N, group, stringsAsFactors = FALSE)
df$id <- factor(df$id, levels=df$id[order(df$group, -df$N)])
df
# id N group
# 1 1 1 A
# 2 2 2 A
# 3 3 1 A
# 4 4 5 A
# 5 5 2 A
# 6 6 3 B
# 7 7 15 B
# 8 8 4 B
# 9 9 15 C
# 10 10 1 C
df$id
# [1] 1 2 3 4 5 6 7 8 9 10
# Levels: 4 2 5 1 3 7 8 6 9 10