[Rd] max/min of NULL gives MININT/MAXINT instead of -INF/+INF (PR#1283)

[gregory_r_warnes@groton.pfizer.com]

R Version 1.4.0 Patched (2002-01-23)
Solaris 5.8

I just noticed that max(NULL) gives a strange result:

	> max(NULL)
	[1] -2147483647
	Warning message: 
	no finite arguments to min/max; returning extreme. in: max(...,
na.rm = na.rm) 

I discovered this when I did something like

	max(object$element)

for an incorrect element name.  The warning  message was helpful, but I was
still surprised to get a negative integer from this operation.  

In playing around, I see that using numeric summary operations on NULL or
numeric(0) gives inconsistent results:

For NULL:

	> max(NULL)
	[1] -2147483647
	Warning message: 
	no finite arguments to min/max; returning extreme. in: max(...,
na.rm = na.rm) 

	> min(NULL)
	[1] 2147483647
	Warning message: 
	no finite arguments to min/max; returning extreme. in: min(...,
na.rm = na.rm) 

	> mean(NULL)
	[1] NA
	Warning message: 
	argument is not numeric or logical: returning NA in:
mean.default(NULL) 

	> sum(NULL)
	[1] 0

	> range(NULL)
	[1] NA NA
 

For numeric(0):

	> max(numeric(0))
	[1] -Inf
	Warning message: 
	no finite arguments to min/max; returning extreme. in: max(...,
na.rm = na.rm) 

	> min(numeric(0))
	[1] Inf
	Warning message: 
	no finite arguments to min/max; returning extreme. in: min(...,
na.rm = na.rm) 

	> mean(numeric(0))
	[1] NaN

	> sum(numeric(0))
	[1] 0
	
	> range(numeric(0))
	[1] NA NA


I'm not sure that it really makes sense return the extremes when min/max are
called with numeric(0) or NULL arguments.  It seems that returning NA in all
of these cases (including sum) would be best, since such operations usually
indicate an error of some sort.

Still, if one insists that min/max should return the extremes, when they
operate on NULL they should at least return the floating point +INF / -INF
so that things don't get really strange when they get compared with floating
point numbers.

-Greg






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