Re: MatrixForm odd behaviour

• To: mathgroup at smc.vnet.net
• Subject: [mg124509] Re: MatrixForm odd behaviour
• From: DrMajorBob <btreat1 at austin.rr.com>
• Date: Sun, 22 Jan 2012 07:22:14 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201201211021.FAA10265@smc.vnet.net>

```> And, since this sets the display on a global
> basis rather than an expression by expression basis, there is no
> need to change the expression to control the display.
> Consequently, the issue with MatrixForm is eliminated.

And, consequently, viewing matrices of anything but trivial size becomes
hopeless.

Bobby

On Sat, 21 Jan 2012 04:21:08 -0600, Bill Rowe <readnews at sbcglobal.net>
wrote:

> On 1/19/12 at 5:08 AM, roby.nowak at gmail.com (roby) wrote:
>
>> As a similar Question is discussed on the group now.
>
>> The following issue:
>
>> When entering e.g.: Dot[MatrixForm[{{1, 0}, {0, 2}}],
>> MatrixForm[{{1, 0}, {0, 2}}]] Mathematica does not evaluate the Dot
>> operation and displays the two unchanged input matrices seperated by
>> a "Dot" each respectively wrapped by MatrixForm, so far so good (or
>> perhaps not so good).
>
>
> The purpose of MatrixForm, TraditionalForm etc is to control the
> display of an individual expression. This is accomplished in
> Mathematica by changing the Head of an expression. That is:
>
> In[6]:= a = MatrixForm[b = RandomReal[1, {5, 5}]];
>
> In[7]:= Head /@ {a, b}
>
> Out[7]= {MatrixForm,List}
>
> In[8]:= MatrixQ /@ {a, b}
>
> Out[8]= {False,True}
>
> So, since Mathematica sees the output of MatrixForm as not a
> matrix it should be no surprise Mathematica won't evaluate
> MatrixForm[m].MatrixForm[m].
>
> The simple way to have matrices and other expressions display
> the way you see in text books is to set your preferences for
> output cells to use TraditionalForm. Once this is done, all
> matrices display nicely with no further effort on your part or
> use of MatrixForm. And, since this sets the display on a global
> basis rather than an expression by expression basis, there is no
> need to change the expression to control the display.
> Consequently, the issue with MatrixForm is eliminated.
>
>

--
DrMajorBob at yahoo.com

```

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