Document Unitful.jl compatibility

[asinghvi17]

This is super low priority, I just tried it out on a lark.

julia> using Rasters, RasterDataSources, ArchGDAL, Unitful
julia> masked_precip = Raster(WorldClim{Climate}, :prec; month = 6)
julia> Quantity.(masked_precip, u"mm")
ERROR: DimensionError: -32768 and 32767 mm are not dimensionally compatible.
Stacktrace:
 [1] _le
   @ ~/.julia/packages/Unitful/GYzMo/src/quantities.jl:243 [inlined]
 [2] <=(x::Quantity{Int16, NoDims, Unitful.FreeUnits{…}}, y::Quantity{Int16, 𝐋, Unitful.FreeUnits{…}})
   @ Unitful ~/.julia/packages/Unitful/GYzMo/src/quantities.jl:233
 [3] <=(x::Int16, y::Quantity{Int16, 𝐋, Unitful.FreeUnits{(mm,), 𝐋, nothing}})
   @ Unitful ~/.julia/packages/Unitful/GYzMo/src/quantities.jl:235
 [4] _fix_missingval(::Type{Quantity{Int16, 𝐋, Unitful.FreeUnits{(mm,), 𝐋, nothing}}}, missingval::Int16)
   @ Rasters ~/.julia/dev/Rasters/src/array.jl:355
 [5] rebuild(A::Raster{…}, data::Matrix{…}, dims::Tuple{…}, refdims::Tuple{}, name::Symbol, metadata::Metadata{…}, missingval::Int16)
   @ Rasters ~/.julia/dev/Rasters/src/array.jl:85
 [6] rebuild
   @ ~/.julia/dev/DimensionalData/src/array/array.jl:85 [inlined]
 [7] copy(bc::Base.Broadcast.Broadcasted{DimensionalData.DimensionalStyle{…}, Tuple{…}, Type{…}, Tuple{…}})
   @ DimensionalData ~/.julia/dev/DimensionalData/src/array/broadcast.jl:47
 [8] materialize(bc::Base.Broadcast.Broadcasted{DimensionalData.DimensionalStyle{…}, Nothing, Type{…}, Tuple{…}})
   @ Base.Broadcast ./broadcast.jl:903
 [9] top-level scope
   @ REPL[130]:1
Some type information was truncated. Use `show(err)` to see complete types.

[rafaqz]

I use Rasters of units all the time. Its just your missingval

Use replace_missing first (except that broadcast fails on missing anyway)

Or @d macro you can set new missingval as a keyword

[rafaqz]

This works fine:

julia> Raster([1.0, 2.0, missing], (X(),), missingval=missing) .* u"mm"
╭─────────────────────────────────────────────────────────────────────────────────╮
│ 3-element Raster{Union{Missing, Quantity{Float64, 𝐋, Unitful.FreeUnits{(mm,), 𝐋, 
nothing}}},1} │
├─────────────────────────────────────────────────────────────────────────── dims ┤
  ↓ X
├───────────────────────────────────────────────────────────────────────── raster ┤
  extent: Extent(X = (1, 3),)
  missingval: missing
└─────────────────────────────────────────────────────────────────────────────────┘
 1.0 mm
 2.0 mm
       missing

Or to use some other missingval this works:

julia> @d Raster([1.0, 2.0, 0.0], (X(),), missingval=0.0) .* u"mm" missingval=0.0u"
mm"
╭────────────────────────────────────────────────────────────────────────────────╮
│ 3-element Raster{Quantity{Float64, 𝐋, Unitful.FreeUnits{(mm,), 𝐋, nothing}},1} │
├────────────────────────────────────────────────────────────────────────── dims ┤
  ↓ X
├──────────────────────────────────────────────────────────────────────── raster ┤
  extent: Extent(X = (1, 3),)
  missingval: 0.0 mm
└────────────────────────────────────────────────────────────────────────────────┘
 1.0 mm
 2.0 mm
 0.0 mm

[rafaqz]

Hmm maybe we should document the units/missingval interaction a bit better. It wont be as important when missing is the default but still kinda needed