[How to plot a simple function]

I have seen examples of data providers, but I have not seen one that allows to plot simple functions.  For example, how do I plot something like:

f(x) = sin(x)

[Allow drag along one axis]

I already figured out how to edit a point's location by setting allow drag's boolean value to true.  However, I haven't figured out how to allow drag but only along one axis.  For example, I would like to change the Y-value only when I drag a point.  Is this possible?  If so, how?