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Merged
merged 2 commits into from
Oct 16, 2021
Merged

Faster computation of quantiles in describe #2909

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528d8a4
Faster computation of quantiles in `describe`
nalimilan Oct 15, 2021
c9c249b
More general approach
nalimilan Oct 15, 2021
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21 changes: 17 additions & 4 deletions src/abstractdataframe/abstractdataframe.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -703,10 +703,23 @@ function get_stats(@nospecialize(col::Union{AbstractVector, Base.SkipMissing}),
d = Dict{Symbol, Any}()

if :q25 in stats || :median in stats || :q75 in stats
q = try quantile(col, [.25, .5, .75]) catch; (nothing, nothing, nothing) end
d[:q25] = q[1]
d[:median] = q[2]
d[:q75] = q[3]
# types that do not support basic arithmetic (like strings) will only fail
# after sorting the data, so check this beforehand to fail early
T = eltype(col)
if isconcretetype(T) && !hasmethod(-, Tuple{T, T})
d[:q25] = d[:median] = d[:q75] = nothing
else
mcol = Base.copymutable(col)
if :q25 in stats
d[:q25] = try quantile!(mcol, 0.25) catch; nothing; end
end
if :median in stats
d[:median] = try quantile!(mcol, 0.50) catch; nothing; end
end
if :q75 in stats
d[:q75] = try quantile!(mcol, 0.75) catch; nothing; end
end
end
end

if :min in stats || :max in stats
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2 changes: 1 addition & 1 deletion test/dataframe.jl
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Expand Up @@ -668,7 +668,7 @@ end
nothing, nothing, nothing],
min = [1.0, 1.0, "a", "a", Date(2000), 1],
q25 = [1.75, 1.5, nothing, nothing, nothing, nothing],
median = [2.5, 2.0, nothing, nothing, nothing, nothing],
median = [2.5, 2.0, nothing, nothing, VERSION >= v"1.7.0-beta1.2" ? Date(2002) : nothing, nothing],
q75 = [3.25, 2.5, nothing, nothing, nothing, nothing],
max = [4.0, 3.0, "d", "c", Date(2004), 2],
nunique = [nothing, nothing, 4, 3, 4, 2],
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