log scale

hi all:

i have a DISPLAY that shows my data points very close to each other.
and as a result tom suggested i use logarithm scale along the x and y axis.
I have studied the example in the Test11.java, but that deals with polar
i am asking if the visad API has a constructor for such a scale;
something like,
if i want to use the log scale for my data (mass,pi), the constructor
details like in Test11.java below:

RealTupleType cartesian = new RealTupleType(x, y); 
    PolarCoordinateSystem polar_coord_sys = 
      new PolarCoordinateSystem(cartesian);