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Re: question about matrix

  • To: mathgroup at smc.vnet.net
  • Subject: [mg63846] Re: [mg63832] question about matrix
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Thu, 19 Jan 2006 00:02:42 -0500 (EST)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

m={{a[1,1],0,a[1,3],0,a[1,5]},
      {a[2,1],0,a[2,3],0,a[2,5]},
      {a[3,1],0,a[3,3],0,a[3,5]},
      {0,0,0,0,0},
      {a[5,1],0,a[5,3],0,a[5,5]}};

fm=Transpose[Select[Transpose[
        Select[m,Union[#]!={0}&]],
      Union[#]!={0}&]]

{{a[1, 1], a[1, 3], a[1, 5]}, {a[2, 1], a[2, 3], 
   a[2, 5]}, {a[3, 1], a[3, 3], a[3, 5]}, 
  {a[5, 1], a[5, 3], a[5, 5]}}

fm==Transpose[DeleteCases[Transpose[
        DeleteCases[m,{(0)..}]],{(0)..}]]

True

fm==Transpose[Transpose[m/.
          {(0)..}:>Sequence[]]/.
      {(0)..}:>Sequence[]]

True


Bob Hanlon

> 
> From: "Tun Myint Aung" <tma at nus.edu.sg>
To: mathgroup at smc.vnet.net
> Subject: [mg63846] [mg63832] question about matrix
> 
> 
> Dear Mathgroup,
> 
>     I have a matrix and it may have rows and columns which are zeros. I
> can drop the rows and columns manually but it is troublesome. So my
> question is that how to drop the rows and columns that are zeros
> automatically.
> 
> Best Regards,
> 
> Tun Myint Aung
> Graduate Student
> National University of Singapore
> E1A #02-18
> Kent Ridge, 119260, Singapore
> E-mail g0202015 at nus.edu.sg <mailto:g0202015 at nus.edu.sg>
> 
> 
> 
> 
> 


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