[Feature Request] QQ plot

[bvenn]

QQ plots allow to compare two sample distributions if:

• a. the underlying population distribution is unknown or if
• b. the relationship between two distributions should be evaluated in greater detail than just their estimated parameters

The following features should be added:

• Adding a function to generate QQ-plots for two sample sequences.
• Adding a function to generate QQ-plots for a sample sequence and a given distribution.
  • You'll need the inverse CDF method for determining quantiles from distributions. These have to be implemented in the Distribution type or specialized functions incorporate these information (e.g. qqPlotGauss).
• optional: add a confidence band

[bvenn]

I've just added QQ plot methods in https://github.com/fslaborg/FSharp.Stats/commit/8145747dd366e4233cdc11bc81d50d950f6bfe36 and a small documentation in https://github.com/fslaborg/FSharp.Stats/commit/f4adbdf1c99d7aa8772c3f35e89720ed1ba04dff. Since major additions were necessary, I'll add unit tests for the inverse error function prior to merging.