[Rd] Changing function arguments to NULL

[Prof Brian Ripley]

On Mon, 28 Feb 2005, McGehee, Robert wrote:

> But passing list(NULL) or NULL into a function may have entirely
> different results.

For a replacement operator expecting a list, list(NULL) *is* what you 
want.  BTW, this is FAQ 7.1.

> foo <- alist(x = 5, y = 2, z = 3)
> foo["x"] <- list(NULL)
> foo
$x
NULL

$y
[1] 2

$z
[1] 3

if (as I guess) you want to set the default value to NULL, not `the 
argument to NULL'.

[...]

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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