Inexact error for histogram2d

[CorySimon]

Julia, v0.5.1

Works:

myplot = plot(x=rand(10), y=rand(10), Geom.histogram2d,
                       Guide.xlabel("y, true"), Guide.ylabel("y, predicted"))

Throws InexactError().

myplot = plot(x=rand(10), y=ones(10), Geom.histogram2d,
                       Guide.xlabel("y, true"), Guide.ylabel("y, predicted"))

My guess is that the error lies in a place where one bin along a certain axis has all of the values.

ERROR: InexactError()
 in trunc(::Type{Int64}, ::Float64) at ./float.jl:463
 in choose_bin_count_2d(::Array{Float64,1}, ::Array{Float64,1}, ::Int64, ::Int64, ::Int64, ::Int64) at /Users/csimon/.julia/v0.5/Gadfly/src/bincount.jl:257
 in apply_statistic(::Gadfly.Stat.Histogram2DStatistic, ::Dict{Symbol,Gadfly.ScaleElement}, ::Gadfly.Coord.Cartesian, ::Gadfly.Aesthetics) at /Users/csimon/.julia/v0.5/Gadfly/src/statistics.jl:620
 in apply_statistics(::Array{Gadfly.StatisticElement,1}, ::Dict{Symbol,Gadfly.ScaleElement}, ::Gadfly.Coord.Cartesian, ::Gadfly.Aesthetics) at /Users/csimon/.julia/v0.5/Gadfly/src/statistics.jl:38
 in render_prepare(::Gadfly.Plot) at /Users/csimon/.julia/v0.5/Gadfly/src/Gadfly.jl:760
 in render(::Gadfly.Plot) at /Users/csimon/.julia/v0.5/Gadfly/src/Gadfly.jl:819
 in display(::Base.REPL.REPLDisplay{Base.REPL.LineEditREPL}, ::MIME{Symbol("text/html")}, ::Gadfly.Plot) at /Users/csimon/.julia/v0.5/Gadfly/src/Gadfly.jl:1113
 in macro expansion at ./multimedia.jl:143 [inlined]
 in display(::Gadfly.Plot) at /Users/csimon/.julia/v0.5/Gadfly/src/Gadfly.jl:1065
 in hookless(::Media.##7#8{Gadfly.Plot}) at /Users/csimon/.julia/v0.5/Media/src/compat.jl:14
 in render(::Media.NoDisplay, ::Gadfly.Plot) at /Users/csimon/.julia/v0.5/Media/src/compat.jl:27
 in display(::Media.DisplayHook, ::Gadfly.Plot) at /Users/csimon/.julia/v0.5/Media/src/compat.jl:9
 in macro expansion at ./multimedia.jl:143 [inlined]
 in display(::Gadfly.Plot) at /Users/csimon/.julia/v0.5/Gadfly/src/Gadfly.jl:1069
 in print_response(::Base.Terminals.TTYTerminal, ::Any, ::Void, ::Bool, ::Bool, ::Void) at ./REPL.jl:154
 in print_response(::Base.REPL.LineEditREPL, ::Any, ::Void, ::Bool, ::Bool) at ./REPL.jl:139
 in (::Base.REPL.##22#23{Bool,Base.REPL.##33#42{Base.REPL.LineEditREPL,Base.REPL.REPLHistoryProvider},Base.REPL.LineEditREPL,Base.LineEdit.Prompt})(::Base.LineEdit.MIState, ::Base.AbstractIOBuffer{Array{UInt8,1}}, ::Bool) at ./REPL.jl:652
 in run_interface(::Base.Terminals.TTYTerminal, ::Base.LineEdit.ModalInterface) at ./LineEdit.jl:1579
 in run_interface(::Base.Terminals.TTYTerminal, ::Base.LineEdit.ModalInterface) at /Applications/Julia-0.5.app/Contents/Resources/julia/lib/julia/sys.dylib:?
 in run_frontend(::Base.REPL.LineEditREPL, ::Base.REPL.REPLBackendRef) at ./REPL.jl:903
 in run_repl(::Base.REPL.LineEditREPL, ::Base.##950#951) at ./REPL.jl:188
 in _start() at ./client.jl:363
 in _start() at /Applications/Julia-0.5.app/Contents/Resources/julia/lib/julia/sys.dylib:?

[tlnagy]

This is related to #860. It looks like it's being caused by a divide-by-zero operation here:

Gadfly.jl/src/bincount.jl

Line 257 in 63a0c28

j = max(1, min(dy, 1 + (@compat floor(Int, (y - y_min) / wy))))

.

It seems as though the bin computation assumes that y_max and y_min are not equal.

[CorySimon]

@tlnagy Maybe a good default is to set the number of bins to be one in that axis if there is no variance in the data along that axis (min = max) and then choose the bin width to be 1.0? I suppose choosing the bin width is arbitrary and could be misleading, though.

[tlnagy]

Apparently, it isn't quite that simple because it looks like the extents of the y axis isn't being computed properly. So some other modifications will be necessary to get this working.

[Mattriks]

A possible workaround:

y=ones(20)
y[1:2] += [-1, 1]*0.1
p = plot(x=rand(20), y=y, Geom.histogram2d(ybincount=1))