AW: AW: Re: Transpose matrix does not work when MatrixForm is used, why?
- To: mathgroup at smc.vnet.net
- Subject: [mg45298] AW: AW: [mg45288] Re: Transpose matrix does not work when MatrixForm is used, why?
- From: Klamser at t-online.de
- Date: Mon, 29 Dec 2003 00:22:06 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
Hi, for your purpose
(m = { {1, 2, 3}, {4, 5, 6} }) // MatrixForm;
is the best!
Where lies the problem positioning a pair of brackets?
Regards
Peter
-----Ursprüngliche Nachricht-----
Von: Dr Bob [mailto:drbob at bigfoot.com]
Gesendet: Sonntag, 28. Dezember 2003 20:42
An: Klamser at t-online.de; mathgroup at smc.vnet.net
Betreff: Re: AW: [mg45288] Re: Transpose matrix does not work when
MatrixForm is used, why?
I don't want to see EVERY matrix in MatrixForm -- it takes up too much
space on my screen, especially for a large matrix, where the screen isn't
even wide enough to see a row in that format.
Also, MatrixQ will test true for something I think of as a list of lists
(not a matrix).
Furthermore, MatrixForm is NOT a primitive. Mathematica doesn't have
primitives as such.
Bobby
On Sun, 28 Dec 2003 18:24:55 +0100, <Klamser at t-online.de> wrote:
> Hi,
>
> every modern computer program solves two problems:
>
> 1. The main problem (Mathematica solve mathematical problems)
>
> 2. Tell the user something about the found solution: The output!
>
> Ancient computer program did not! They only solved the problem, the
> output
> option was forgotten (ALGOL in the early sixties... ;-) => (because there
> was not enough memory...).
>
> The MatrixForm primitive is not a mathematical problem, it is one of the
> second kind. Output has something to do with tradition, not so deep with
> the
> problem itself...
>
> Therefore the output primitives should not be locked with the problem
> itself.
>
> Some people want to have the same format each Mathematica session.
> Therefore
> you find by some experts
>
> http://www.verbeia.com/mathematica/tips/Tricks.html
>
> or
>
> http://www.verbeia.com/mathematica/tips/HTMLLinks/Tricks_174.html
>
> $PrePrint=Which[MatrixQ[#],MatrixForm[#],NumberQ[#],#,True,Short[#,50]]&
>
> Putting this into your init.m file in the kernel directory, you will have
> never again to type //MatrixForm and you never have again to position the
> brackets correct:
>
> (m = { {1, 2, 3}, {4, 5, 6} }) // MatrixForm;
>
> Regards
>
> Peter
>
>
> -----Ursprüngliche Nachricht-----
> Von: Bobby R. Treat [mailto:drbob at bigfoot.com]
> Gesendet: Sonntag, 28. Dezember 2003 11:11
> An: mathgroup at smc.vnet.net
> Betreff: [mg45288] Re: Transpose matrix does not work when MatrixForm is
> used, why?
>
>
> THANKS for emphasizing that MatrixForm and List are two different
> heads. That's very, very true -- but rather obvious and not
> particularly helpful.
>
> The issue is that the MatrixForm "wrapper" affects evaluation,
> contrary to the description in Help. The question is what to do about
> it.
>
> Thanks to Andrzej Kozlowski, we have a short answer that seems to
> work.
>
> Bobby
>
> Klamser at t-online.de wrote in message news:<bsjlej$24e$1 at smc.vnet.net>...
>> Hi,
>>
>> why has Santa Claus a red cape on?
>>
>> A deer is not a dog is not a dog.
>>
>> A MatrixForm Object is not a Matrix.
>>
>> m = { {1, 2, 3}, {4, 5, 6} } // MatrixForm;
>> ??m -> m = MatrixForm[{{1, 2, 3}, {4, 5, 6}}]
>>
>> Therefore m[[0]] -> MatrixForm
>>
>> But
>>
>> (m = { {1, 2, 3}, {4, 5, 6} }) // MatrixForm;
>> ??m -> m = {{1, 2, 3}, {4, 5, 6}}
>>
>> Therefore m[[0]] -> List
>>
>> Therefore again:
>>
>> A MatrixForm Object is not a Matrix.
>>
>> Regards
>>
>> Peter Klamser
>>
>>
>> -----Ursprüngliche Nachricht-----
>> Von: steve_H [mailto:nma124 at hotmail.com]
>> Gesendet: Mittwoch, 24. Dezember 2003 23:42
>> An: mathgroup at smc.vnet.net
>> Betreff: Re: Transpose matrix does not work when MatrixForm is
>> used, why?
>>
>>
>> Dr Bob <drbob at bigfoot.com> wrote in message
>> news:<bsbmsb$lr1$1 at smc.vnet.net>...
>>
>> > That may be easier... if we are willing to constantly pay attention to
>> > whether the target of Transpose is "wrapped" in MatrixForm or not.
>> > (Transpose/@m if it's wrapped, Transpose@m if not.)
>> >
>> > But if we want Help's claim that evaluation is not affected to be true
> (it
>> > currently is NOT), then we have to redefine Transpose, Inverse, etc.
>> as
> in
>> > my example.
>> >
>> > Only then would MatrixForm act properly as a wrapper, as intended.
>> >
>> > Bobby
>> >
>>
>>
>> > On Tue, 23 Dec 2003 18:38:10 +0900, Andrzej Kozlowski
> <akoz at mimuw.edu.pl>
>> > wrote:
>> >
>> > > This of course works, but presumably he would want do this for other
>> > > functions, (e.g. Inverse etc), not just transpose. So it seems to me
> it
>> > > is easier simply to use Map:
>> > >
>> > > m = { {1, 2, 3}, {4, 5, 6} } // MatrixForm
>> > > Transpose/@m
>> > >
>> > > etc.
>> > >
>> > > Andrzej Kozlowski
>> > >
>>
>>
>> Correct Dr Bob,
>>
>> But why do we have to resort to all these tricks? Why can't Mathematica
> just
>> accept a MatrixForm (or any other representation form) of the object
>> in its functions (Transpose in this example) just as well as the
>> list representation?
>>
>> Each Mathematica function, where needed, could start by checking if this
>> 'Wrapper' as you call it exists, and converts it to a list
>> representation (remove the wrapper), and do its thing on the list,
>> and at the end put the 'wrapper' around the result as needed and
>> return the result to the user?
>>
>> This way one does not have to worry which form of an object one uses,
>> the representation form or the list form.
>>
>> i.e. representation form will be transparent to all Mathematica
>> functions.
>