Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2009

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: MatrixForm affects values instead of only printing

  • To: mathgroup at smc.vnet.net
  • Subject: [mg100368] Re: [mg100298] MatrixForm affects values instead of only printing
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Tue, 2 Jun 2009 06:42:12 -0400 (EDT)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <200905311035.GAA16937@smc.vnet.net>
  • Reply-to: murray at math.umass.edu

Nothing wrong or inconsistent there. Look at:

   FullForm[test2]
MatrixForm[List[-3,7,5]]

Then, as expected:

   test2[[1]]
{-3,7,5}

And so the 3rd element of that is...

   test2[[1]][[3]]
5

... which is the same result as from:

   test2[[1, 3]]

The MatrixForm is still lurking there, as you'll see if you evaluate:

   Head[test2]
MatrixForm

Nothing has "changed"!

summer wrote:
> Here is the example:
> 
> test1={-3, 7, 5}
> test1[[3]]
> 
> returns the list and 5 as expected;
> 
> test2={-3, 7, 5}//MatrixForm
> test2[[3]]
> 
> returns a column vector and error: "part 3 of blah blah doesn't exist". The actual list itself is test2[[1]]. To get the right 3rd element I have to do:
> 
> test2[[1,3]]
> 
> which returns 5 as expected.
> 
> 
> The problem is MatrixForm is NOT supposed to change the expression it is applied on according to the manual. Is that a bug or there's logical explanation?
> 

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305


  • Prev by Date: Re: Re: comments on Wolfram Alpha
  • Next by Date: Re: comments on Wolfram Alpha
  • Previous by thread: Re: MatrixForm affects values instead of only printing
  • Next by thread: Sidebar Tools