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MathGroup Archive 2002

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Re: MatrixForm Oddity

  • To: mathgroup at
  • Subject: [mg35692] Re: MatrixForm Oddity
  • From: "John Doty" <jpd at>
  • Date: Fri, 26 Jul 2002 04:16:35 -0400 (EDT)
  • Organization: Wampler-Doty Family
  • References: <ahodv5$bs9$>
  • Sender: owner-wri-mathgroup at

In article <ahodv5$bs9$1 at>, BobHanlon at wrote:

> In a message dated 7/24/02 3:20:33 AM, siegman at writes:
>>Construct a matrix which has symbol  a  in the upper left (1,1) element
>>and symbols  I c  in the rest of the top row and the left-most column,
>>dot it into itself three times, and display the result using MatrixForm.
>>The top row in the display now has  I c (a^2 - 4c^2) ; the left-most 
>>column now has  I a^2 c - 4 I c^3 .  Not exactly a serious problem, but
>>not exactly clean either.  Makes it harder to see at a glance whether a
>>given matrix is symmetric above the diagonal (could be a problem in a 
>>more complicated situation).  Could possibly mess up the behavior of 
>>pattern matching rules?
> use Simplify
> m.m.m // Simplify

Or Expand[]. It's not a MatrixForm[] thing: it's present no matter what
output form you use. Mathematica doesn't automatically expand products.
The construction of your matrix elements proceeds by different paths (sum
of products versus product of sums), so they look different.

| John Doty		"You can't confuse me, that's my job."
| Home: jpd at
| Work: jpd at

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