hiding columns and area-avg

[Mark Perks <perks@umbc.edu>]

	There's two important features I'd like to understand about,
	or add to, siag.

1.  How can I get area-avg (or r_avg) to ignore cells with no values?
    I use siag for student grades and I want to average scores for
    only those students taking the exam and ignore blanks for students
    who missed it.

    I see in siag.scm that (define (area-avg r1 c1 r2 c2) has the atom
    (if (number? val).  What does this mean if not "if val is a
    number?"  Why are blank cells getting averaged as zeroes?

2.  Is there any way to hide columns?  I've grown fond of this feature
    in Lotus 123 or xspread so I can print out just selected columns
    for posting of grades.

    Also ... can anyone recommend a good introduction to scheme?  I'm
    pretty good with Emacs lisp but many atoms in the various *.scm
    files are unknown to me.


    My sincere thanks to anyone who can help me with these questions.

	       Mark


       *,,,,/\o__ H. Mark Perks      Dept of Chem,  UMBC  9,
       perks@umbc.edu  410 455-2789  Baltimore, MD 21250  <\