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MathGroup Archive 1995

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Re: Help on use of Packages

  • Subject: [mg2187] Re: Help on use of Packages
  • From: danl (Daniel Lichtblau)
  • Date: Fri, 13 Oct 1995 06:23:58 GMT
  • Approved: usenet@wri.com
  • Distribution: local
  • Newsgroups: wri.mathgroup
  • Organization: Wolfram Research, Inc.
  • Sender: daemon at wri.com ( )

In article <45d1te$63m at ralph.vnet.net> zheng at risky.ecs.umass.edu (Yuan  
Zheng) writes:
> Hi, 
> 
> I have the following problem when I use the  
LinearAlgebra`MatrixManipulation
> Package. I also use Math2.2 for DOS and wnmath2.2 notebook. All of them  
have
> the same result.
> 
> I am new to the Mathematica. Are there something I am doing wrong? I  
followed
> the exact procedure described on pp 218-219 in the book Guide to  
Standard
> Mathematica Packages Version 2.2.
> 
> I need to do a lot of matrix manipulations in my symbolic computation.  
Could
> somebody help me to solve this problem?
> 
> 
> Thanks
> 
> 
> Yuan Zheng
> Dept of Mechanical Engineering
> Umass, Amherst
> 
> 
> 
> The following is the screen display.
> 
> 
> 
> ===============================================
> Mathematica 2.2 for DEC RISC
> Copyright 1988-93 Wolfram Research, Inc.
>  -- Terminal graphics initialized -- 
> 
> In[1]:= 
> In[2]:= a = {{a11,a12},{a21,a22}}//MatrixForm 
> Out[2]//MatrixForm= a11   a12
> 
>                     a21   a22
> 
> In[3]:= b = {{b11,b12},{b21,b22}}//MatrixForm
> Out[3]//MatrixForm= b11   b12
> 
>                     b21   b22
> 
> In[4]:= cc = AppendColumns[a,b]//MatrixForm
> Out[4]//MatrixForm= AppendColumns[a11   a12, b11   b12]
> 
>                                   a21   a22  b21   b22
> 
> In[5]:= Dimensions[cc]
> Out[5]= {1}
> 
> In[6]:= dd = AppendRows[a,b]//MatrixForm
> Out[6]//MatrixForm= AppendRows[a11   a12, b11   b12]
> 
>                                a21   a22  b21   b22
> 
> In[7]:= Dimensions[dd]
> Out[7]= {1}
> 
> In[8]:= ee = BlockMatrix[ { {a,b},{b, {{0,0},{0,0}}}}]//MatrixForm
> Out[8]//MatrixForm= 
>  
>     AppendColumns[AppendRows[a11   a12, b11   b12], 
> 
> >                            a21   a22  b21   b22
>      
>     >   AppendRows[b11   b12, {{0, 0}, {0, 0}}]]
> 
>                    b21   b22
> 
> In[9]:= Dimensions[ee]
> Out[9]= {1}
> 
> In[10]:= Quit
> 

  The problem is that // has higher precedence than = and hence it gets  
put on the matrix as a head before the set assignment is done. That is,   
you do
In[55]:= a = {{a11,a12},{a21,a22}}//MatrixForm
Out[55]//MatrixForm= a11   a12

                     a21   a22

and you get something with Head of MatrixForm:
In[56]:= FullForm[a]
Out[56]//FullForm= MatrixForm[List[List[a11, a12], List[a21, a22]]]

If instead you do, say,
In[57]:= (aa = {{a11,a12},{a21,a22}})//MatrixForm 
Out[57]//MatrixForm= a11   a12

                     a21   a22

then you get what you want.
In[58]:= FullForm[aa]
Out[58]//FullForm= List[List[a11, a12], List[a21, a22]]


  Daniel Lichtblau, WRI
  danl at wri.com




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