anchor.diff:  
   In this section, we look at various features of the F# data frame library (using both
   `Series` and `Frame` types and modules). Feel free to jump to the section you are interested
  -in, but note that some sections refer back to values built in "Createing & loading".
  +in, but note that some sections refer back to values built in "Creating & loading".
   
   You can also get this page as an [F# script file](https://github.com/BlueMountainCapital/FSharp.DataFrame/blob/master/samples/features.fsx)
   from GitHub and run the samples interactively.
  
positive.code: // Add new series from a list of values
  people?Siblings <- [0; 2; 1; 3]
  
  // Repalce existing series with new values
  // (Equivalent to people?Siblings <- ...)
  people.ReplaceSeries("Siblings", [3; 2; 1; 0])
  
  
negative.code: country list, we generate a series that contains individual countries and the count
  of visits (this is done by composing `Seq.countBy` and a function `series` to build
  a series of observations). Then we turn the result to a data frame and fill missing
  values with the constant zero (see a section about [handling missing values](#missing)).
  
  ### Grouping data frames
  
  