ggplot2 boxplot for each variable with unequal distance

Question

I have the following data frame:

  date       DGS1MO DGS3MO DGS6MO DGS1 DGS2 DGS3 DGS5 DGS7 DGS10 DGS20 DGS30
1 2006-02-28   4.47   4.62   4.74 4.73 4.69 4.67 4.61 4.57  4.55  4.70  4.51
2 2006-03-31   4.65   4.63   4.81 4.82 4.82 4.83 4.82 4.83  4.86  5.07  4.90
3 2006-04-28   4.60   4.77   4.91 4.90 4.87 4.87 4.92 4.98  5.07  5.31  5.17
4 2006-05-31   4.75   4.86   5.08 5.07 5.04 5.03 5.04 5.06  5.12  5.35  5.21
5 2006-06-30   4.54   5.01   5.24 5.21 5.16 5.13 5.10 5.11  5.15  5.31  5.19
6 2006-07-31   5.02   5.10   5.18 5.11 4.97 4.93 4.91 4.93  4.99  5.17  5.07

Using melt (from reshape2) I got this data frame:

 date        variable value
1 2006-02-28   DGS1MO  4.47
2 2006-03-31   DGS1MO  4.65
3 2006-04-28   DGS1MO  4.60
4 2006-05-31   DGS1MO  4.75
5 2006-06-30   DGS1MO  4.54
6 2006-07-31   DGS1MO  5.02

As you can see I have 1, 3, 6 month, along with 10, 20, 30 year time horizons. I would like to plot box-and-whisker plot for each of these columns and have the following code:

bwplot <- ggplot(df, aes(x = variable, y = value, color = variable)) +
    stat_boxplot(geom = "errorbar") +
    geom_boxplot() +
bwplot

However, the issue is the distance (space) between the boxplots for each variable is the same. Ideally, there should be very small distance between the boxplots for 1 month and 3 month. And the gap between the boxplots for 10 year and 20 year should be wide. To remedy, I have tried to convert the variables into numbers (1/12, 3/12, 6/12, 1, 2, etc.) and then tried this code:

levels(df$variable) <- c(0.83, 0.25, 0.5, 1, 2, 3, 5, 7, 10, 20, 30)

bwplot <- ggplot(df, aes(x = as.numeric(as.character(df$variable)), y = value, color = variable)) +
    stat_boxplot(geom = "errorbar") +
    geom_boxplot() +
bwplot

But what I am getting is only one huge boxplot for the entire time horizon followed by this warning msg:

Warning messages:
1: Continuous x aesthetic -- did you forget aes(group=...)?

If I try

group = variable

I get

Error: Continuous value supplied to discrete scale

What is the right way of doing this?

Thanks.

Jean Jean · Accepted Answer · 2016-12-22T08:47:26

s<-data.frame(date=seq(as.Date("2006-02-01"), by="month", length.out=6), M1=rnorm(6,5,0.5), M3=rnorm(6,5,0.5), M6=rnorm(6,5,0.5), Y1=rnorm(6,5,0.5), Y2=rnorm(6,5,0.5), Y3=rnorm(6,5,0.5), Y10=rnorm(6,5,0.5), Y20=rnorm(6,5,0.5), Y30=rnorm(6,5,0.5))

require(ggplot2)
require(reshape2)
s.melted<-melt(s, id.var="date")

#Create an axis where the numbers represent the number of months elapsed
s.melted$xaxis <-c("M"=1, "Y"=12)[sub("(M|Y)([0-9]+)","\\1",s.melted$variable)] * as.numeric(sub("(M|Y)([0-9]+)","\\2",s.melted$variable))

s.melted[sample(1:nrow(s.melted),6),]
         date variable    value xaxis
23 2006-06-01       Y1 4.645595    12
38 2006-03-01      Y10 5.190710   120
25 2006-02-01       Y2 4.831788    24
50 2006-03-01      Y30 3.892580   360
39 2006-04-01      Y10 4.513831   120
31 2006-02-01       Y3 4.357127    36

# Only show the ticks for variable
bwplot <- ggplot(s.melted, aes(x = xaxis, y = value, color = variable)) +
  stat_boxplot(geom = "errorbar") +
  geom_boxplot()  + scale_x_continuous(breaks=s.melted$xaxis,
                                     labels=s.melted$variable)
bwplot

ggplot2 boxplot for each variable with unequal distance

1 Answers