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Topic: Work on Basic Mathematica Stephen!
Replies: 81   Last Post: Jun 4, 2013 5:59 AM

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Murray Eisenberg

Posts: 2,105
Registered: 12/6/04
Re: Work on Basic Mathematica Stephen!
Posted: May 19, 2013 5:46 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

Yes, it's a very basic fact that there's no linear ordering of the complex numbers compatible with the field operations. (It's an often-assigned exercise in a first course in complex analysis.)

(Note though, that the coefficients of the imaginary parts of complex numbers form the real field, which is ordered as usual.)

But I don't see the relevance of that to needing a Chop facility. The point remains that complex methods are often used to solve strictly real problems, but due to roundoff resulting form working with approximate numbers, you may obtain a complex result with tiny imaginary part that you wish to disregard. That's what Chop does.
On May 18, 2013, at 2:38 AM, Peter Klamser <klamser@googlemail.com> wrote:

> http://mathworld.wolfram.com/ComplexNumber.html says:
> "Unlike real numbers, complex numbers do not have a natural ordering,
> so there is no analog of complex-valued inequalities. This property is
> not so surprising however when they are viewed as being elements in
> the complex plane, since points in a plane also lack a natural
> ordering."
>
> Peter
>
> 2013/5/17 Andrzej Kozlowski <akozlowski@gmail.com>:

>>
>> On 16 May 2013, at 09:28, Peter Klamser <klamser@googlemail.com> wrote:
>>

>>> This is an interesting discussion. But if it can be useful, we have to
>>> make short proposals. Nobody has the time to read long texts.
>>>
>>> A) First proposal: Identify useless or false constructions in Mathematica
>>>
>>> aa) Eliminating Chop[] for complex numbers. Complex numbers are
>>> oderless and therefore nobody call estimate, weather the distance of 1
>>> + 10^-google i to the real numbers is small or big.

>>
>> You are mistaken. The issue of order and the issue of distance are entirely different and unrelated. The complex numbers are a one dimensional complex Hilbert space with the standard inner product, hence a (complete) metric space. The distance between two complex numbers is well defined and so it the distance of a complex number from the real line. Also, it would be crazy if Mathematica itself decided that complex numbers which are sufficiently close to the real line are actually real one. This sort of thing should be left to the user (obviously!) and this is exactly what Chop does (it has a second argument, you know).
>> If I understand your suggestion correctly, it is probably the worst suggestion for an "improvement" in Mathematica I have ever read on this forum.
>> Fortunately, it is 100% sure that it will be ignored as all such suggestions usually are.
>>
>> Andrzej Kozlowski
>>
>>

>>> Chop[] is the
>>> result of Mathematica design, that it presents often complex results, where
>>> real values are the simpler result and can be reached by
>>> ComplexExpand[].
>>> The simplest solution is always the best solution.
>>>
>>> B) Mathematica should be integrated seamless in Tex without using copy and
>>> paste. The should be the cell type Tex, and the printout and save
>>> modus Tex, where all other cells are suppressed.
>>>
>>> Peter
>>>
>>>
>>>
>>> 2013/5/15 Szabolcs Horv=E1t <szhorvat@gmail.com>:

>>>>
>>>> While some individual points are debatable, I also completely agree
>>>> with David's main message. Mathematica needs more focus, particularly
>>>> some work on stability and robustness. Even if it would come at a cost
>>>> of new features (there are many features I'd like to see, but you can't
>>>> have everything).
>>>>
>>>> Re: "if I click in an existing Input cell and do a line return the
>>>> Messages window opens with a contact WRI if this happens message"
>>>>
>>>> This bug (on OS X) is really annoying when typing code in another
>>>> language in a Mathematica string. If will sometimes completely ruin
>>>> the typed text if I press return several times while inside a string.
>>>> It's a bit ironic that this bug appeared in the same release which
>>>> brought us RLink (which I'm using these days, i.e. I'm typing a lot of
>>>> R code inside Mathematica strings).
>>>>
>>>> On 2013-05-12 07:28:34 +0000, djmpark said:

>>>>> (I've renamed this and started a new thread because my reply is not exactly
>>>>> to the question.)
>>>>>
>>>>> Oh, what a wonderful Wolfram blog! Earlier Stephen hinted at Mathematica as
>>>>> an iPhone app. Now it's data mining Facebook data (Gee I wonder if
>>>>> Zuckerberg has thought of that? He might be able to develop a great business
>>>>> model.) Can Twitter be far behind? There are many significant mathematical
>>>>> equations that will fit into 64 characters - or whatever the limit is.
>>>>> Ramanujan would probably have done well on Twitter. And women are more
>>>>> interested in personal relationships and men are more interested in sports?
>>>>> Who would have thought? The average person on Facebook has 342 friends

> ! Well
>>>>> there are friends and there are friends. Montaigne wrote that his friendship
>>>>> with Etienne de La Bo=E9tie was such that "So many coincidences are needed to
>>>>> build [it up] that it is a lot if fortune can do it once in three
>>>>> centuries." One might say, ephemera in ephemera out.
>>>>>
>>>>> For the dwindling few of us who still have desktop computers and large
>>>>> screens, or maybe two large screens, who are interested in learning ordoing
>>>>> some extended mathematics, and the even fewer who would like to write
>>>>> literate Mathematica notebooks as technical documents, I wonder if Stephen
>>>>> could find some time to attend to basic Mathematica, fixing its problems and
>>>>> fulfilling its vision?
>>>>>
>>>>> Mathematica lacks stability. Things that worked fine in one version don't
>>>>> work in the next. Especially troubling to me is the basic user interface

>>

---
Murray Eisenberg murray@math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower phone 413 549-1020 (H)
University of Massachusetts 413 545-2838 (W)
710 North Pleasant Street fax 413 545-1801
Amherst, MA 01003-9305








Date Subject Author
5/12/13
Read Work on Basic Mathematica Stephen!
David Park
5/13/13
Read Re: Work on Basic Mathematica Stephen!
psycho_dad
5/13/13
Read Re: Work on Basic Mathematica Stephen!
psycho_dad
5/14/13
Read Re: Work on Basic Mathematica Stephen!
Nasser Abbasi
5/15/13
Read Re: Work on Basic Mathematica Stephen!
szhorvat@gmail.com
5/16/13
Read Re: Work on Basic Mathematica Stephen!
szhorvat@gmail.com
5/16/13
Read Re: Work on Basic Mathematica Stephen!
Dr. Peter Klamser
5/17/13
Read Re: Work on Basic Mathematica Stephen!
Andrzej Kozlowski
5/17/13
Read Re: Work on Basic Mathematica Stephen!
Murray Eisenberg
5/17/13
Read Re: Work on Basic Mathematica Stephen!
Dr. Peter Klamser
5/18/13
Read Re: Work on Basic Mathematica Stephen!
Dr. Peter Klamser
5/19/13
Read Re: Work on Basic Mathematica Stephen!
Murray Eisenberg
5/19/13
Read Re: Work on Basic Mathematica Stephen!
paulmchale7@gmail.com
5/19/13
Read Re: Work on Basic Mathematica Stephen!
paulmchale7@gmail.com
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Read Re: Work on Basic Mathematica Stephen!
szhorvat@gmail.com
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Read Re: Work on Basic Mathematica Stephen!
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5/29/13
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fd
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