CODEWITHSUNDEEP
rggplot2levels
ejg
ejg

Reputation: 196

Order x-axis elements in barchart by two columns

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

Upvotes: 0

Views: 1079

Answers (1)

Ven Yao
Ven Yao

Reputation: 3710

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

Upvotes: 1

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