Cannot use NullableArray in a data frame

[nalimilan]

I see this with latest master of DataFrames and NullableArrays:

julia> DataFrame(y=NullableArray([1,2]))
ERROR: MethodError: `upgrade_vector` has no method matching upgrade_vector(::NullableArrays.NullableArray{Int64,1})
 in setindex! at /home/milan/.julia/DataFrames/src/dataframe/dataframe.jl:368
 in DataFrame at /home/milan/.julia/DataFrames/src/dataframe/dataframe.jl:104

I suspect I'm missing something, since people seem to be doing this all the time (e.g. JuliaData/DataFramesMeta.jl#42).

[amellnik]

To anyone else who sees a similar error and ends up here: DataFrames with NullableArray columns need to be constructed all at once, and can't currently have additional columns added. This means that while you can do things like:

DataFrame(Any[NullableArray([1,2])], Symbol[:y])

to construct a DataFrame, you can't subsequently add more columns with something like

df[:col] = NullableArray([1,2])

LoadError: MethodError: `upgrade_vector` has no method matching upgrade_vector(::NullableArrays.NullableArray{Int64,1})
while loading In[9], in expression starting on line 2

 in setindex! at C:\Users\amellnik\.julia\v0.4\DataFrames\src\dataframe\dataframe.jl:368

If you have a DataFrame with NullableArrays for columns and you need to add columns or otherwise convert it to a vanilla DataFrame (with DataArray columns) you can use something like

function NullableDFtoDF!(ndf)
    for c in names(ndf)
        ndf[c] = DataArray(ndf[c].values, ndf[c].isnull)
    end
end

function DFtoNullableDF(df)
    DataFrame(Any[NullableArray(df[c].data,
        Array{Bool}(df[c].na)) for c in names(df)], names(df))
end

[nalimilan]

See #1008.