The world is full of ever-cleverer packages which generate ever more chartjunk. Rain is not one of these! It is philosophically aligned to Tufte’s principles of maximizing the visibility of data, and refusing to permit spurious decorations, artificial 3D effects and unnecessary ink such as grids and moiré-shadings. See “The Visual Display of Quantitative Information” (Graphics Press 1983) for some excellent background reading on good chart design.

There are three steps required to produce a completed graphic, although for really simple charts, steps 1 and 3 may not be needed.

1. Set up the plotting space
2. Plot the data
3. Add any notes and extra datum lines

Stage-1 includes defining all the headings, labels and captions, as any of these operations may influence the shape of the final plotting region. A typical sequence of commands might be:

   ch.Set 'Heading' 'This is my Graph'
   ch.Set 'Key' 'Budget,Actual'
   ch.Plot mydata
   ch.Note 'May figures are low because ...' (12 56)
   PG„ch.Close
   View  PG    © To see it on the screen

Note how the plotting commands work on a high-level description of the finished graphic to produce a set of simple drawing commands (in a subset of the PostScript language) which is returned to you by ch.Close. This is actually just a simple character vector, and you can browse it in the workspace with the standard APL editor.

To see the completed chart on the screen, you must View it (obviously, you might have several charts stacked up in advance with different names): the View function runs a simplified PostScript interpreter to render the chart on the screen. You can also print it, either via normal Windows channels or direct to your PostScript printer if you have one.

Because PostScript allows scaling and translation of any graphic, you can also take a set of such charts and easily combine them ‘4-up’ on the page – see the functions ABOVE and BESIDE in the RainPro workspace, together with the example Climate composite for some ideas.