Histogram bars become line when many observations?

Specific Domains Visualization
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1

I noticed that when there are a lot of (e.g. 10 million) observations, histogram produces a line plot instead of a bar plot:

using Distributions, StatsPlots
x = rand(Normal(), 1_000_000)
histogram(x, bins = -5:0.2:5, label = "x")
savefig("x.png")

x

y = rand(Normal(), 10_000_000)
histogram(y, bins = -5:0.2:5, label = "y")
savefig("y.png")

y

The same thing happens when I pass in normalize = true. Is this behavior intentional? Is there a way to turn it off, i.e. force there to be bars? I’m using Distributions v0.21.11 and StatsPlots v0.13.0.

2

It does not look like it
https://github.com/JuliaPlots/Plots.jl/blob/3459bcd81766f71ba6ff0d185bf9e32cc5425521/src/recipes.jl#L679
Maybe you can manually specify seriestype to be barhist instead of calling histogram?

2 Likes
3

Yes, calling plot(x, seriestype = :barhist) did it for me - thanks!

2 Likes
4

Exactly. It’s a bit of an overmagic compromise stemming from that me and @oschulz couldn’t agree on which of those two should be the default, coming from scientific fields with very different usual n.

3 Likes
6

Yes - I had originally proposed to use stephist as the default, because it works for few and very many bins, but bar-style histograms seemed to be too popular to not make them the default. But maybe this magic should depend on the number of bins, not the number of observations? @mkborregaard, what do you think?

The ideal solution, long term, would be to have something like a filled step hist with lines between the bins as the default, and make the lines between the bins thinner/weaker as the bin count increases, until they finally vanish if there are very many bins. This way, we’d have a smooth transition between both styles as the default.

3 Likes
7

I agree it’s better to bar it on the number of bins, but in the current implementation the series type is chosen before autobins are calculated

8

in the current implementation the series type is chosen before autobins are calculated

Ah, right, that was the reason!