Please add support for the function 'PERCENTRANK'.
Please see Yegor's ApacheCon talk for details on how to go about adding new functions to the formula evaluator: http://people.apache.org/~yegor/apachecon_us2010/Evaluation_Of_Excel_Formulas_In_POI.pptx Please do send in a patch if you get something working!
https://support.office.com/en-us/article/PERCENTRANK-function-F1B5836C-9619-4847-9FC9-080EC9024442 This function looks like it is used to determine what percentile a given number is within a data set. It also looks like it is an OOXML-only formula.
Added with r1892077 - will look at PERCENTRANK.INC and PERCENTRANK.EXC in next few weeks.