Re: Row or column?

*To*: mathgroup at smc.vnet.net*Subject*: [mg112737] Re: Row or column?*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Wed, 29 Sep 2010 04:11:39 -0400 (EDT)

I don't see where the problem is -- provided you use a proper data structure for a matrix and don't confuse that with the display you get from MatrixForm. For example, you get exactly the expected mathematical results from: a = {{2,3}}; a.Transpose[a] Transpose[a].a Note: {Dimsnsions[a], Dimensions@Transpose[a]} { {1,2}, {2,1} } On 9/28/2010 6:02 AM, Kevin J. McCann wrote: > This lack of distinction between rows and columns can be a problem. > Consider: > > a.Transpose[a] and Transpose[a].a > > Kevin > > On 9/27/2010 5:48 AM, Sjoerd C. de Vries wrote: >> Sam, >> >> Mathematica considers the first level of a list as rows, the second, >> nested, levels are the columns etc. So, for display purposes {{a, b}} >> would show as a row, but if you want to use it for matrix/vector >> multiplication you only need {a,b}, as Mathematica does not >> differentiate between row or column vectors. >> >> Cheers -- Sjoerd >> >> On Sep 26, 8:44 am, Sam Takoy<sam.ta... at yahoo.com> wrote: >>> Hi, >>> >>> How come >>> >>> {a, b} // MatrixForm >>> {{a}, { b}} // MatrixForm >>> >>> produce identical outputs: columns? >>> >>> I would think that the first "matrix" is 1x2 and the second is 2x1. >>> >>> Alternatively, how do I produce a 1x2 matrix? >>> >>> Many thanks in advance, >>> >>> Sam >> >> > -- 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