Adds several points to each of the scatter plot point curves.
sp - the scatter plot context
xx - array of pointers that point to arrays containing the new x coordinates for each curve.
yy - array of pointers that point to arrays containing the new y points for each curve.
n - number of points being added, each represents a subarray of length dim where dim is the value from
The new points will not be displayed until a call to
PetscDrawSPDraw() is made