It happens, that the required GIS-Functions aren’t in the used GIS-System. Sometimes it’s possible to use license extentions with costs for those additional functions.
Another option is to integrate downloaded free plugins or scripts. You can also install another GIS- system, where the desired functions are available. This solutions work for GIS- experts very well.
GIS- user, who work rare with GIS and don’t know for example how to integrate plugins and which alternative GIS- systems are available, have more problems. They easily find approaches and ideas in the internet, but still have the problems named above.
The best way to solve this problems is to integrate the needed functions in a special application (for instance a simualtion model). If this is not possible, an alternative approach is to develop a special gis tool, which prepare input data for your application in the best way.
Here you find examples with a free downloadlink: