How to adjust the X-axis order of boxplot with StatsPlots.jl

Specific Domains Visualization
,
1 
using Plots, StatsPlots, DataFrames

df = DataFrame(
    id=repeat([3, 17, 21], inner=10),
    value=randn(30)
)

@df df boxplot(string.(:id), :value, fillalpha=0.75, linewidth=1)

The result is
image

I want the box to be 3, 17, 21 from left to right.

PS: I have also tried CategoricalArray for the id column, but nothing changed.

1 Like
2

Normally you can just pass id as the x values, but then the boxes will be in the correct numerical positions.
In this case here, the best is probably just to replace 3, 17 and 21 with 1, 2 and 3 change the xticks to show 3, 17 and 21 - or to pad the values (they are sorted alphabetically)

@df df boxplot(lpad.(string.(:id), 2), :value, fillalpha=0.75, linewidth=1)
1 Like
3

Thanks. I figured out a similar solution today (by replacing original id values with properly lexicographically ordered ones) but it seemed a little ugly and introduced unnecessary noise.

It is much better if there is some option like order to specify the order directly.

4

What syntax would you suggest for that?

5

For this type of problem, @sprintf is our best friend:

using Plots, StatsPlots, DataFrames, Printf

df = DataFrame(
    id=repeat([3, 17, 21], inner=10),
    value=randn(30)
)

str = [ @sprintf("%02i", x) for x in df.id ] 
@df df boxplot(str, :value, fillalpha=0.75, linewidth=1)

# or to keep similar syntax, one may define a sprintf02i() function:
sprintf02i(vecx) = [ @sprintf("%02i", x) for x in vecx ] 
@df df boxplot(sprintf02i(:id), :value, fillalpha=0.75, linewidth=1)

StatsPlot_Boxplot_lexicographic_order

1 Like
6

I personally prefer

lpad.(string.(:id), 2)

to

str = [ @sprintf("%02i", x) for x in df.id ]

but that’s a question of taste I guess

2 Likes
8

@mkborregaard, sorry for having overlooked your answer, much simpler indeed.

1 Like
9

Hi, @mkborregaard, I have no knowledge of internal details. But how about

@df df boxplot(string.(:id), :value, fillalpha=0.75, linewidth=1, xorder=[3, 17, 21])

Or we may pass into a custom sort function to sort the specific column in a df.

@df df boxplot(string.(:id), :value, fillalpha=0.75, linewidth=1, 
                         xsort=sort)

The above two lpad and sprintf workarounds work well for this particular example. But what if I want the order to be 21 3 17? Of course, I can still find a workaround, but it does not look beautiful.

1 Like
10

I happened to work a bit with boxplots yesterday. It would be really nice if there was a recipe for Pair{String, AbstractArray} so you could make a boxplot from ["a"=>[1,5,9], "b"=>[7,7,19]]. I might just write one.

11

@Shuhua, the folllowing seems to work by left-right padding spaces, if elegance is not a concern:

using Plots, StatsPlots, DataFrames

df = DataFrame(
    id=repeat([3, 17, 21], inner=10),
    value=randn(30)
)
xorder = [21 3 17]
Nx = length(xorder)
str = fill("",length(df.id))
for (i,xi) in enumerate(xorder)
    j = findall(x->x==xi, df.id)
    si = " "^(Nx-i)
    @. str[j] = si * string(df.id[j]) * si
end

# solution by left-right space-padding strings
@df df boxplot(str, :value, fillalpha=0.75, linewidth=1)

StatsPlot_Boxplot_lexicographic_order3

1 Like