Passing a seq<float option> from F# to RProvider

Question

I want to be able to pass a sequence of option float to the RProvider in F# . If I have a sequence of floats with Some float and None , how can I get the None values into R with the RProvider ? I would have expected the None s would be equivalent to an NA value in R , but I can't get pass a seq<option float> to R.

For example, with

open System
open RDotNet
open RProvider
open RProvider.graphics
open RProvider.stats  

let optData4 = 
    seq [Some 10.0; Some 9.0; Some 8.0; None; Some 6.0; 
        Some 5.0; Some 5.0; None; Some 4.0; Some 2.0; 
        None]

let testData4 = 
    namedParams [
        "regPrice", optData4;]
    |> R.data_frame

I get a multi-line error:

System.Exception: No converter registered for type Microsoft.FSharp.Collections.FSharpList`1[[Microsoft.FSharp.Core.FSharpOption`1[[System.Double, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]], FSharp.Core, Version=4.4.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]] or any of its base types
>    at RProvider.RInteropInternal.convertToR@164.Invoke(String message) in C:\Tomas\Public\bmc\FSharp.RProvider\src\RProvider\RInterop.fs:line 164
   at RProvider.RInteropInternal.REngine.SetValue(REngine this, Object value, FSharpOption`1 symbolName) in C:\Tomas\Public\bmc\FSharp.RProvider\src\RProvider\RInterop.fs:line 274
   at RProvider.RInteropInternal.toR(Object value) in C:\Tomas\Public\bmc\FSharp.RProvider\src\RProvider\RInterop.fs:line 287
   at RProvider.RInterop.passArg@447(List`1 tempSymbols, Object arg) in C:\Tomas\Public\bmc\FSharp.RProvider\src\RProvider\RInterop.fs:line 461
   at RProvider.RInterop.argList@468-1.GenerateNext(IEnumerable`1& next) in C:\Tomas\Public\bmc\FSharp.RProvider\src\RProvider\RInterop.fs:line 469
   at Microsoft.FSharp.Core.CompilerServices.GeneratedSequenceBase`1.MoveNextImpl()
   at Microsoft.FSharp.Core.CompilerServices.GeneratedSequenceBase`1.System-Collections-IEnumerator-MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at Microsoft.FSharp.Collections.SeqModule.ToArray[T](IEnumerable`1 source)
   at RProvider.RInterop.callFunc(String packageName, String funcName, IEnumerable`1 argsByName, Object[] varArgs) in C:\Tomas\Public\bmc\FSharp.RProvider\src\RProvider\RInterop.fs:line 466
   at <StartupCode$FSI_0012>.$FSI_0012.main@() in C:\Users\sranney\repositories\carolina_refit_bits\refit_bits\refit_bits\RDemo.fs:line 102
Stopped due to error

The only way I can pass anything to the RProvider is if I convert the seq<option float> to a seq<float> with

let optData4 = 
    seq [Some 10.0; Some 9.0; Some 8.0; None; Some 6.0; 
        Some 5.0; Some 5.0; None; Some 4.0; Some 2.0; 
        None]
    |> Seq.choose id

let testData4 = 
    namedParams [
        "regPrice", optData4;]
    |> R.data_frame

but this negates the purpose of having the option of None (which, I would have thought would be comparable to R s NA value.

How can I pass a sequence of values to the RProvider where some of the values are None in F# and should be NA in R ?

Answer 1

You can do it with Deedle and nullable values:

let toNullable =
       function
       | None -> Nullable()
       | Some x -> Nullable(x)

let optData4 = 
    seq [Some 10.0; Some 9.0; Some 8.0; None; Some 6.0; 
        Some 5.0; Some 5.0; None; Some 4.0; Some 2.0; 
        None] 
    |> Seq.map(toNullable)

let series = Series.ofNullables(optData4)

let testData4 = 
    namedParams [
        "regPrice", series;]
    |> R.data_frame

Answer 2

I think you should be able to do this just be replacing the None values with nan (this is not entirely right, because in R NA and NaN are different, but there is no way to express two different non-values for a float in F#):

let optData4 = 
    [ 10.0; 9.0; 8.0; nan; 6.0; 5.0; 5.0; nan; 4.0; 2.0; nan ]

let testData4 = 
    namedParams [
        "regPrice", optData4;]
    |> R.data_frame

I have not tested this, but I think this is what we do in Deedle internally.