Hi Anyi,
There are various extension points that will enable new calculations to be plugged into the client using custom code.
New aggregations and column calculations will allow different statistics to be calculated on graph axes or in calculated columns (e.g. geometric mean). The SpotfireDeveloper.CalculationMethodExample example in the SDK has a couple of examples of calculations and aggregations.
More sophisticated distributions or probability functions could be implemented using the custom curve fit extension point (I've used these in other industries to calculate and draw a Gaussian fit and to show various six sigma reference lines):
See http://stn.spotfire.com/stn/Tasks/CreatingFittingModel.aspx
Then there is a generic CustomCalculation extension point that allows data tables or columns to be used as input, and provides complete flexibility for any sort of calculation, with the results being stored as one or more columns or tables. There are some basic examples in the SDK, in the project SpotfireDeveloper.CalculationToolExample. The same extension point is used to hook in the S+ client or server in a custom example e.g. SpotfireDeveloper.SPlusConsoleExample. There is some additional explanation on the STN again at:
http://stn.spotfire.com/stn/Tutorials/HowToIntegrateSpotfireAndSPlusClient.aspx and
http://stn.spotfire.com/stn/Tutorials/HowToIntegrateSpotfireAndSPlusServer.aspx
That last interface is totally generic though and you have full flexibility to implement any algorithm you want.