pillar3D: Create a 3D pillar chart to display (x, y, z) data coordinate surface.
Description
Give data on x, y, z coordinate values of a 3D surface, this function
plots them after making pillars near each z value by adding and
subtracting small amounts dz. Instead of pins of the height z this
creates pillars which better resemble a surface. It uses the
wireframe() function of `lattice' package to do the plotting.