Stacia Varga shows how you can parameterize your R scripts within Power BI:
It’s not difficult, but the cool thing about Power BI is that I can use parameters to dynamically change the report visualization without opening up the script. To do this:
Open the Query Editor in Power BI
Click Manage Parameters, and then click New Parameter.
Set the parameter properties – Name, Type, and Current Value.The Name is how I will reference the parameter my R script, the Type is the data type, and Current Value is the initial value that I want to set (if any).
Click through for an example and more details.