Hi,
I guess you need to look at the graphic part of the MIDP as a poor mans
java AWT library. You need to build some high level modules like bar, histogram
of the underlying drawRectangle, line, string etc.
You may use existing examples from the java sdk, or go search the web for
some plot applets and see if they present some usable drawing modules.
It will take some years before we get high level graphics components like the
ones you may find in java2.