added refPeriod to RDF representation
added refPeriod in query and analysis description
added package "stringr)
removed whitespaces from RDF strings
resolved wrong output of mean and median (confused these two values)
- debugged issue with more than four datasets
- problem occurs at SPARQL package -> r doesn't get any value (wasn't able to resolve problem)
added more datasets to selection list
added user input verification for datasets and refAreas
changed legend position of plot from horizontal to vertical and changed size of plot title
title of datasets and refAreas are now being added dynamically and shown as a tooltip