java.lang.NullPointerException
at edu.cens.spatial.RTileController.getTileValues(RTileController.java:109)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at RJavaTools.invokeMethod(RJavaTools.java:386)
Error in osmtile(x%%nX, y, zoom, type) :
could not obtain tile: 3952 2654 13
The best place to ask this sort of question is either in issues on the GitHub repo, or possibly in an R forum or GIS StackExchange. The OSM community are relatively unlikely to use R to create maps as there are many other available tools.