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