adding values from a csv column and getting the mean. beginner help

[Chris Angelico]

On Thu, Dec 12, 2013 at 7:00 AM, Mark Lawrence <breamoreboy at yahoo.co.uk> wrote:
> I use the alternative X for a mandatory argument X.

Also common, but how do you specify a keyword, then? Say you have a
command with subcommands:

$0 foo x y
Move the foo to (x,y)
$0 bar x y z
Go to bar X, order a Y, and Z it [eg 'compress', 'gzip', 'drink']

How do you show that x/y/z are mandatory args, but foo/bar are
keywords to be typed exactly? In some formats italicized text can make
that distinction, but not in pure text.

ChrisA