Breaks the window into an rows-by-cols matrix of small axes, selects the index-th subplot for the current plot, and returns the handle. The subplots are counted along the top row of the window, then the second row, etc.

subplot(index) selects the index-th subplot for the current plot, and returns the handle, assuming it is already created.

Here is a typical example: 

	require "lab"
	w=gfx.Window(300,500) 
	w:subplot(1,2,1)
	w:hist(lab.randn(100,3))
	w:subplot(2)
	w:plot({5,7,8,1,3},'co:')