Set a WaterLevelDataFrame's slot riverSource:
A function to set the slot
river of an object of class
an object of class WaterLevelDataFrame.
a new value of class
valuehas to have a length of one and has to be Elbe or Rhine.
The function above sets a new
value for the slot
and returns an object of class WaterLevelDataFrame. Since
river is a slot relevant for the computation of the
w is set to
NA and needs to be recomputed by functions like