Deedle: errors using Frame.mapColValues

Question

I'm following a tutorial:
http://dkowalski.com/blog/archive/2014/01/11/f-deedle-and-computational-investing.aspx
and when I try to apply normalization to all the columns of "stocks" Frame, using Frame.mapColValues, I obtain the following error message:

System.InvalidOperationException: OptionalValue.Value: Value is not available in Deedle.OptionalValue``1.get_Value() in c:\Tomas\Public\Deedle\src\Deedle\Common\Common.fs:riga 35 in FSI_0046.normalized@52-8.Invoke(ObjectSeries``1 os) in C:\Users\Bruno-Astarita\Documents\Visual Studio 2013\Projects\TestDeedle02\TestDeedle02\TestTutorial01.fsx:riga 52 in <StartupCode$Deedle>.$Series.f@257-13[K,V,R](Func``3 f, Int32 i, K key, V v) in c:\Tomas\Public\Deedle\src\Deedle\Series.fs:riga 358 in <StartupCode$Deedle>.$Series.newVector@354-1.Invoke(Int32 i, Tuple``2 tupledArg) in c:\Tomas\Public\Deedle\src\Deedle\Series.fs:riga 355 in Microsoft.FSharp.Collections.IEnumerator.mapi@129.DoMoveNext(b& ) in Microsoft.FSharp.Collections.IEnumerator.MapEnumerator``1.System-Collections-IEnumerator-MoveNext() in Microsoft.FSharp.Collections.SeqModule.ToArray[T](IEnumerable``1 source) in Microsoft.FSharp.Collections.ArrayModule.OfSeq[T](IEnumerable``1 source) in Deedle.Series``2.Select[R](Func``3 f) in c:\Tomas\Public\Deedle\src\Deedle\Series.fs:riga 352 in Deedle.Series``2.Select[R](Func``2 f) in c:\Tomas\Public\Deedle\src\Deedle\Series.fs:riga 365 in Deedle.SeriesModule.MapValues[T,R,K](FSharpFunc``2 f, Series``2 series) in c:\Tomas\Public\Deedle\src\Deedle\SeriesModule.fs:riga 451 in <StartupCode$FSI_0046>.$FSI_0046.main@() in C:\Users\Bruno-Astarita\Documents\Visual Studio 2013\Projects\TestDeedle02\TestDeedle02\TestTutorial01.fsx:riga 49 Stopped due to error

I tried to find the problem making a step-by-step procedure based on source code in FrameModule.fs, and the error raises at the instruction Series.mapValues f. Where I'm wrong?
Many thanks.

Update
After many tests, the problem seems be arised by the row let firstItem = osAsFloat.GetAt(0) from the tutorial. If I try to substitute it with let firstItem = 2.0 everything is ok. Still is not clear for me this behaviour.

Answer 1

Finally I found the reason of problem. In some Series in the Frame, there are missing values in correspondence to the first element. If I do not use those Series, everything is ok.