reducing over an empty collection is not allowed; consider supplying init to the reducer #87
Description
I have a date vector (originally from CSV.read) on which extrema fails, see below
Interestingly when I copy the data, things work. I.e. extrema(dd[1:end]) works
below is an MWE.
julia> using Dates
julia> using DataFrames
julia> using CSV
julia> #p = CSV.read(raw"C:\temp\ori2c.csv",DataFrame,dateformat="dd.mm.yyyy",copycols=true,stringtype=String,pool=false);
julia> fi = raw"https://gist.githubusercontent.com/kafisatz/e64a61727d8817a4433cecf17144dd55/raw/f49241d0d6b177c10d23809750b1c7af21f53adf/ori2c.csv";
julia> p = CSV.read(download(fi),DataFrame,dateformat="dd.mm.yyyy",copycols=true,stringtype=String,pool=false);
julia> addtldf=DataFrame(a=String[],date=Date[],b=Int[],c=Int[],date2=Date[]);
julia> append!(p,addtldf);
julia> extrema(p.date)
ERROR: MethodError: reducing over an empty collection is not allowed; consider supplying `init` to the reducer
Stacktrace:
[1] reduce_empty(op::Base.MappingRF{Base.ExtremaMap{typeof(identity)}, typeof(Base._extrema_rf)}, #unused#::Type{Date})
@ Base .\reduce.jl:356
[2] reduce_empty_iter
@ .\reduce.jl:379 [inlined]
[3] mapreduce_empty_iter(f::Function, op::Function, itr::Vector{Date}, ItrEltype::Base.HasEltype)
@ Base .\reduce.jl:375
[4] _mapreduce
@ .\reduce.jl:427 [inlined]
[5] _mapreduce_dim
@ .\reducedim.jl:365 [inlined]
[6] #mapreduce#765
@ .\reducedim.jl:357 [inlined]
[7] mapreduce
@ .\reducedim.jl:357 [inlined]
[8] #_extrema#791
@ .\reducedim.jl:999 [inlined]
[9] _extrema
@ .\reducedim.jl:999 [inlined]
[10] #extrema#789
@ .\reducedim.jl:995 [inlined]
[11] extrema
@ .\reducedim.jl:995 [inlined]
[12] extrema
@ C:\Users\bernhard.konig\.julia\packages\SentinelArrays\BcfVF\src\chainedvector.jl:793 [inlined]
[13] extrema(x::SentinelArrays.ChainedVector{Date, Vector{Date}})
@ SentinelArrays C:\Users\bernhard.konig\.julia\packages\SentinelArrays\BcfVF\src\chainedvector.jl:787
[14] top-level scope
@ REPL[9]:1
julia> extrema(p.date[1:end])
(Date("2023-02-01"), Date("2023-05-03"))
julia> versioninfo()
Julia Version 1.8.5
Commit 17cfb8e65e (2023-01-08 06:45 UTC)
Platform Info:
OS: Windows (x86_64-w64-mingw32)
CPU: 32 × AMD Ryzen 9 5950X 16-Core Processor
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-13.0.1 (ORCJIT, znver3)
Threads: 16 on 32 virtual cores
Environment:
JULIA_NUM_THREADS = 16
JULIA_EDITOR = "code"
julia>
[a93c6f00] DataFrames v1.5.0
[336ed68f] CSV v0.10.9
[91c51154] SentinelArrays v1.3.18