Richard, your definition is, of course, not valid R code.
I assume the pseudocode is easier to write in a language like python and says
that you want to loop through all items and compare each item to every other
item in a second similar loop (meaning it happens twice and also compares
items to themselves) and take the absolute values of subtracting one from the
other and keep the maximum.
If I am right, this is a bit of overkill for the purpose as it generate O(N^2)
results that are then evaluated for a maximum.
The more straightforward methods are O(N) as they find the smallest and largest
(perhaps in one sweep) and do a subtraction.
Admittedly, if you want a very general solution that includes complex numbers
or quaternions or octonions, it may be needed. But I suspect that for most
common purposes, it won't be worth the effort. And, in any case, I am not sure
how robust the min() function works for some of these cases.
-----Original Message-----
From: R-help <r-help-boun...@r-project.org> On Behalf Of Richard O'Keefe
Sent: Thursday, June 26, 2025 3:50 AM
To: Dennis Fisher <fis...@plessthan.com>
Cc: r-help <r-help@r-project.org>
Subject: Re: [R] Does this exist: diff(range(VAR, na.rm=T))
We can define span(x) another way:
span(x) = max {|a-b| | a \in x, b \in x}
This gives the same result as diff(range(x)) for logical x, integer x,
and double x, but it also works for complex x and in general for any
collection of elements of something that could be seen as a normed
vector spans.
This makes a good example of why it might be a bad idea to jump
prematurely to a definition in base R.
But there is another and more obviously statistical reason. Consider
a time series.
diff(range(..)) makes sense on a (real, complex, multivariate) time
series, but the span of a time series
is more usually thought of as the span of *time* it is measured over.
On Thu, 26 Jun 2025 at 06:11, Dennis Fisher <fis...@plessthan.com> wrote:
>
> Version 4.4.2
> OS X
>
> Colleagues
>
> I often need to determine the span of the x-variable in a graphic.
>
> This is easy to determine with:
> diff(range(VAR, na.rm=T))
>
> I am not aware of any function in base R that accomplishes this and “span” is
> not taken.
>
> Would it be possible to add such a function? Not a major addition but often
> useful.
>
> Dennis
>
> Dennis Fisher MD
> P < (The "P Less Than" Company)
> Phone: 1-415-307-4791
> www.PLessThan.com
>
>
> [[alternative HTML version deleted]]
>
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