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Re: Lists: Row Vectors vs. Column Vectors. (feels like such a silly

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  • Subject: [mg110212] Re: Lists: Row Vectors vs. Column Vectors. (feels like such a silly
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Tue, 8 Jun 2010 07:08:53 -0400 (EDT)

On 6/7/10 at 8:08 AM, rgorka at gmail.com (telefunkenvf14) wrote:

>Can someone explain why a list does not display in MatrixForm as a
>row?---It's ok if the answer is computer sciency. I'll take some
>advil before I attempt to digest any answers. :)

Because a 1D list is not defined as either a row nor a column.
An example of something that displays as a row in MatrixForm
would be

{Range[4]}

Alternatively, something that displays as a column in MatrixForm is:

List/@Range[4]

But note:

In[4]:= MatrixQ /@ {{Range[4]}, List /@ Range[4]}

Out[4]= {True,True}

That is, both of these constructs are seen as matrices by
Mathematica and displayed appropriately by MatrixForm.

Also, notice

In[5]:= a = Range[4];
b = RandomInteger[1, {4, 4}];

In[8]:= b.a

Out[8]= {3,1,8,7}

In[9]:= a.b

Out[9]= {10,5,3,7}

showing it is up to you to determine whether a 1D list should be
interpreted as a column vector or row vector.



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