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[MUG] max element
| [MUG] max element |
|
Author: Maple User Group
Posted: Thu, 13 Feb 2003 09:10:33 -0500
|
>> From: Maple User Group "maple_gr"
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To: "maple-list"
Subject: max element of array
Date: Fri, 31 Jan 2003 08:23:26 +0000
From: "A. van der Meer" "meerawj"
On 1/28/2003 "Jeffrey.Dambacher" wrote:
>
>>> From: "Jeffrey.Dambacher"
>
>-------------------------------------------------------------------
>The problem is to find the maximum value of elements of a given array,
of
>length n, where elements of the array and length vary from one
application
>to another.
>
>A fixed example given here, where
>n:=5:
>w:=array(1..n,[1,4,5,3,2]):
>
>how do I pull out the max value of w without listing each w[j] element of
w
>as above? While I can do it for the above n=5 example with:
>
>max(w[1],w[2],w[3],w[4],w[5]):
>
>If I want to evaluate an array of length 4 or 6, I would have to either
add
>or subtract a w[j] element from the above command. I need to work off
of
>one command for any size of n. It seems that
>
>max(w[1..n]);
>
>or
>
>max(entries(w));
>
>should work, but they does not.
The command
max(op(convert(w,set)));
will work for arrays of all lengths.
Explanation: max( ) requires a sequence of numbers as arguments.
entries(w) returns a sequence if lists that can not simply used as
arguments for max.
A. van der Meer
University of Twente
Dept. of Applied Mathematics
P.O.Box 217 7500AE Enschede
tel 053 489 4293
room WB-N232
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Date: Fri, 31 Jan 2003 11:16:15 -0500 (EST)
From: Carl Devore "devore"
To: "maple-list"
Subject: max element of array
On Tue, 28 Jan 2003 "Jeffrey.Dambacher" wrote:
> how do I pull out the max value of w without listing each w[j] element of w
> as above? While I can do it for the above n=5 example with:
max(map(op, [entries](w))[]);
That gracefully handles the case of undefined entries.
> It seems that
> max(w[1..n]);
> or
> max(entries(w));
> should work, but they does not.
The .. substructure index notatation works with rtables, not arrays. It
is meaningless (but does not generate an error) with arrays. Your attempt
with entries did not work because entries returns each element in
brackets. Mine strips off those extra brackets.
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From: "Dr Francis J. Wright" "F.J.Wright"
To: "Jeffrey.Dambacher"
Subject: max element of array
Date: Fri, 31 Jan 2003 16:21:15 -0000
From: "Jeffrey.Dambacher"
To: "maple-list"
Sent: Tuesday, January 28, 2003 4:54 AM
Subject: [MUG] max element of array
> The problem is to find the maximum value of elements of a given array, of
> length n, where elements of the array and length vary from one application
> to another.
>
> A fixed example given here, where
> n:=5:
> w:=array(1..n,[1,4,5,3,2]):
>
> how do I pull out the max value of w without listing each w[j] element of
w
> as above? While I can do it for the above n=5 example with:
>
> max(w[1],w[2],w[3],w[4],w[5]):
>
> If I want to evaluate an array of length 4 or 6, I would have to either
add
> or subtract a w[j] element from the above command. I need to work off of
> one command for any size of n. It seems that
>
> max(w[1..n]);
>
> or
>
> max(entries(w));
>
> should work, but they does not.
Max requires a *sequence* of values, and neither w[1..n] nor entries(w)
provides a suitable sequence. However, here are some approaches that work:
max(seq(w[i],i=1..n));
max(op(convert(w, set)));
max(op(map(op,{entries(w)})));
max(seq(op(e),e=entries(w)));
It's a moot question whether to use a set or a list as the intermediate data
structure in the middle two cases; in some situations it would matter, but
for maximization it doesn't.
Francis
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From: Stanley J Houghton "S.J.Houghton"
Date: Fri, 31 Jan 2003 16:55:06 +0000
To: "maple-list"
Subject: max element of array
Try
max(convert(w,list)[]);
The brackets [] turns the list into a simple series
of values and max does the rest.
Regards
Stan
On Tue, 28 Jan 2003 15:54:09 +1100
"Jeffrey.Dambacher" wrote:
>
> >> From: "Jeffrey.Dambacher"
>
> Dear Maple User Group,
>
> I was wondering if there was any chance that a question I have regarding
> Maple could be put to the Maple User Group. Please let me know what
> resources are available to me in regards to the below question.
>
> Thanks for any forthcoming help.
>
> Best regards,
>
> Jeffrey Dambacher
> CSIRO Marine Research
> Hobart, Tasmania
> Australia
> "Jeffrey.Dambacher"
>
> -------------------------------------------------------------------
> The problem is to find the maximum value of elements of a given array, of
> length n, where elements of the array and length vary from one application
> to another.
>
> A fixed example given here, where
> n:=5:
> w:=array(1..n,[1,4,5,3,2]):
>
> how do I pull out the max value of w without listing each w[j] element of w
> as above? While I can do it for the above n=5 example with:
>
> max(w[1],w[2],w[3],w[4],w[5]):
>
> If I want to evaluate an array of length 4 or 6, I would have to either add
> or subtract a w[j] element from the above command. I need to work off of
> one command for any size of n. It seems that
>
> max(w[1..n]);
>
> or
>
> max(entries(w));
>
> should work, but they does not.
>
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Date: Fri, 31 Jan 2003 10:57:32 -0800 (PST)
From: Robert Israel "israel"
To: "maple-list"
Subject: max element of array
max expects a sequence (not a list or array) of numbers.
w[1..n] would return the whole list if w was a list, but doesn't work
for an array.
entries(w) produces a sequence, but it's a sequence of lists
[1], [4], [5], [3], [2]
The simplest way is
max(w[j]$j=1..n);
or
max(seq(w[j], j=1..n));
Or you could use
max(op(convert(w, list)));
which has the advantage of not needing to know n.
Or you could use "flatten" from my Maple Advisor Database,
available at <http://www.math.ubc.ca/~israel/advisor>:
max(flatten(w));
Robert Israel "israel"
Department of Mathematics http://www.math.ubc.ca/~israel
University of British Columbia
Vancouver, BC, Canada V6T 1Z2
On Tue, 28 Jan 2003 "Jeffrey.Dambacher" wrote:
> -------------------------------------------------------------------
> The problem is to find the maximum value of elements of a given array, of
> length n, where elements of the array and length vary from one application
> to another.
>
> A fixed example given here, where
> n:=5:
> w:=array(1..n,[1,4,5,3,2]):
>
> how do I pull out the max value of w without listing each w[j] element of w
> as above? While I can do it for the above n=5 example with:
>
> max(w[1],w[2],w[3],w[4],w[5]):
>
> If I want to evaluate an array of length 4 or 6, I would have to either add
> or subtract a w[j] element from the above command. I need to work off of
> one command for any size of n. It seems that
>
> max(w[1..n]);
>
> or
>
> max(entries(w));
>
> should work, but they does not.
>
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Date: Sun, 02 Feb 2003 00:44:43 +0100
From: Helmut Kahovec "helmut.kahovec"
To: "maple-list"
Subject: max element of array
"Jeffrey.Dambacher" wrote:
>| I was wondering if there was any chance that a question I have regarding
>| Maple could be put to the Maple User Group. Please let me know what
>| resources are available to me in regards to the below question.
The following could be a solution to your problem:
> restart;
> MAX:=(w::array)->eval(map(op,'max'(entries(w)))):
> n:=5: w:=array(1..n,[1,4,5,3,2]):
> MAX(w);
5
Helmut
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Date: Mon, 03 Feb 2003 17:15:13 -0800
From: "Setemkia (Fawn) FallingTree" "Fawn"
To: "maple-list"
Subject: max element of array
"Jeffrey.Dambacher" wrote:
>The problem is to find the maximum value of elements of a given array, of
>length n, where elements of the array and length vary from one application
>to another.
>
>A fixed example given here, where
>n:=5:
>w:=array(1..n,[1,4,5,3,2]):
>
>how do I pull out the max value of w without listing each w[j] element of w
>as above? While I can do it for the above n=5 example with:
>
>max(w[1],w[2],w[3],w[4],w[5]):
>
>If I want to evaluate an array of length 4 or 6, I would have to either add
>or subtract a w[j] element from the above command. I need to work off of
>one command for any size of n. It seems that
>
>max(w[1..n]);
>
>or
>
>max(entries(w));
>
>should work, but they does not.
>
I haven't seen a reply posted to this question. I do know why
max(entries(w)) does not work...
Reading the documentation you will find that entries(w) returns a
SEQUENCE of LISTs. I.E.,
[1],[4],[5],[3],[2]
One could use max(op(map(op,[entries(w)])))
however max(op(convert(w,list))) is likely to be more efficient.
Where an indexfn has been used to minimize storage for a sparse
array/matrix use of rtable_elems is most likely more efficient. E.g.:
max(op(map(curry(op,2),rtable_elems(TheRTable))))
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From: "Peter Weigand" "peter.weigand"
To: "maple-list"
Date: Tue, 04 Feb 2003 12:12:43 +0100
Subject: max element of array
On 28 Jan 2003 at 15:54, "Jeffrey.Dambacher" wrote:
> The problem is to find the maximum value of elements of a given array,
> of length n, where elements of the array and length vary from one
> application to another.
>
> A fixed example given here, where
> n:=5:
> w:=array(1..n,[1,4,5,3,2]):
On 28 Jan 2003 at 15:54, "Jeffrey.Dambacher" wrote:
Dear Jeffrey, I think the simplest way is ton convert the array into list and pick with
op-command the elements for the maximum procedure
> w:=array(1..n,[1,4,5,3,2]):
> L:=convert(w,list):
> max(L);
5
Kind regards
Peter-----------------------------------------------------
Dr. Peter Weigand,
Chemnitz University of Technology
Faculty of Mathematics
Mail :D-09107 Chemnitz, Germany
Phone: +49 0371 531 2655
Fax : +49 0371 531 4947
E-mail: "weigand"
_____________________________________________________
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Date: Wed, 12 Feb 2003 15:31:13 +0100
From: PierLuigi Zezza "pierluigi.zezza"
Subject: max element of array
To: "maple-list"
Hi,
this should work
> n:=5;
n := 5
> w:=array(1..n,[1,4,5,3,2]);
w := [1, 4, 5, 3, 2]
> max(op(convert(w, set)));
5
gigi zezza
At 15.54 28/01/2003 +1100, you wrote:
> >> From: "Jeffrey.Dambacher"
>
>Dear Maple User Group,
>
>I was wondering if there was any chance that a question I have regarding
>Maple could be put to the Maple User Group. Please let me know what
>resources are available to me in regards to the below question.
>
>Thanks for any forthcoming help.
>
>Best regards,
>
>Jeffrey Dambacher
>CSIRO Marine Research
>Hobart, Tasmania
>Australia
>
>
>-------------------------------------------------------------------
>The problem is to find the maximum value of elements of a given array, of
>length n, where elements of the array and length vary from one application
>to another.
>
>A fixed example given here, where
>n:=5:
>w:=array(1..n,[1,4,5,3,2]):
>
>how do I pull out the max value of w without listing each w[j] element of w
>as above? While I can do it for the above n=5 example with:
>
>max(w[1],w[2],w[3],w[4],w[5]):
>
>If I want to evaluate an array of length 4 or 6, I would have to either add
>or subtract a w[j] element from the above command. I need to work off of
>one command for any size of n. It seems that
>
>max(w[1..n]);
>
>or
>
>max(entries(w));
>
>should work, but they does not.
My new e-mail address is
"pzezza"
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