R help - Jan 2009 - pmax and sort?

I am having a hard time understanding the documentation and I was wondering if
there would be someone to help clear the cobwebs.

The documentation for pmax states:

pmax and pmin take one or more vectors (or matrices) as arguments and return a
single vector giving the ?parallel? maxima (or minima) of the vectors. The first
element of the result is the maximum (minimum) of the first elements of all the
arguments, the second element of the result is the maximum (minimum) of the
second elements of all the arguments and so on. Shorter inputs are recycled if
necessary. attributes (such as names or dim) are transferred from the first
argument (if applicable).

This descirption seems to me like what sort would return. Would someone please
help me understand the differenece between pmax and sort?

Thank you.

Kevin

I am having a hard time understanding the documentation and I was wondering if
there would be someone to help clear the cobwebs.

The documentation for pmax states:

pmax and pmin take one or more vectors (or matrices) as arguments and return a
single vector giving the ?parallel? maxima (or minima) of the vectors. The first
element of the result is the maximum (minimum) of the first elements of all the
arguments, the second element of the result is the maximum (minimum) of the
second elements of all the arguments and so on. Shorter inputs are recycled if
necessary. attributes (such as names or dim) are transferred from the first
argument (if applicable).

This descirption seems to me like what sort would return. Would someone please
help me understand the differenece between pmax and sort?

Thank you.

Kevin

Here are a couple of quick examples that may help:
> 1:10
 [1]  1  2  3  4  5  6  7  8  9 10
> 10:1
 [1] 10  9  8  7  6  5  4  3  2  1
> pmax( 10:1, 1:10 )
 [1] 10  9  8  7  6  6  7  8  9 10
> pmin( 1:10, 5 )
 [1] 1 2 3 4 5 5 5 5 5 5

In the first example with pmax, there are 2 vectors being compared (10-1, 1-10),
so first 10 is compared to 1 and since 10 is larger it is the first element of
the returned vector, then 9 is compared to 2 and 9 becomes the second element,
this continues till the 10th comparison is 1 vs. 10 and 10 is the final element.
The second (pmin) example shows the recycling, each of the numbers 1-10 is
compared to the number 5, in each case the smaller of the pair is returned (1-4
for the first 4 elements, then 5 for the rest).

Hope this helps,

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of rkevinburton at charter.net
> Sent: Monday, January 12, 2009 5:55 PM
> To: r-help at r-project.org
> Subject: [R] pmax and sort?
> 
> I am having a hard time understanding the documentation and I was
> wondering if there would be someone to help clear the cobwebs.
> 
> The documentation for pmax states:
> 
> pmax and pmin take one or more vectors (or matrices) as arguments and
> return a single vector giving the ?parallel? maxima (or minima) of the
> vectors. The first element of the result is the maximum (minimum) of
> the first elements of all the arguments, the second element of the
> result is the maximum (minimum) of the second elements of all the
> arguments and so on. Shorter inputs are recycled if necessary.
> attributes (such as names or dim) are transferred from the first
> argument (if applicable).
> 
> This descirption seems to me like what sort would return. Would someone
> please help me understand the differenece between pmax and sort?
> 
> Thank you.
> 
> Kevin
> 
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