anchor.diff:    /// entire window contains missing values, the result is 0.
     ///
     /// [category:Moving windows]
  -  static member movingSum size (series:Series<'K, float>) : Series<'K, float> =
  +  static member inline movingSum size (series:Series<'K, 'V>) : Series<'K, float> =
       applyMovingSumsTransform 1 size (fun s -> s.sum) series
   
     /// Returns a series that contains means over a moving window of the specified size.
  
positive.code:   /// entire window contains no values, the result is 0.
    ///
    /// [category:Expanding windows]
    static member expandingSum (series:Series<'K, float>) : Series<'K, float> =
      applyExpandingMomentsTransform (fun w -> w.sum) series
  
    /// Returns a series that contains means over expanding windows (the value for
  
negative.code:   /// entire window contains fewer than 3 values, the result is missing.
    ///
    /// [category:Expanding windows]
    static member inline expandingSkew (series:Series<'K, 'V>) : Series<'K, float> =
      // population -> sample estimate    
      let toEstSkew w = 
        if w.nobs < 3.0 then nan else
  