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structure vs. matrix

7 messages · Edna Bell, Mark Difford, Duncan Murdoch +2 more

Original
Edna Bell
# 
Hi R Gurus!

When creating a matrix, is it better to use the structure function or
the matrix function, please?

Thanks,
Edna Bell
Mark Difford
# 
Hi Edna,
I hope you have a huge (empty) jar in the kitchen, and that your pantry is
empty.

R isn't too difficult, except if you're trying to do stats (and don't know
what you are doing --- though I am not suggesting that you don't know how to
do stats;).

## see
?structure
?matrix

A structure is not a matrix.  So, if you want to make a matrix, use
matrix().  Easy.

HTH,
Mark.
Edna Bell wrote:

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Duncan Murdoch
    

    

      
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On 04/11/2007 1:28 AM, Edna Bell wrote:

            

      
      
      
    

        
I'd use the matrix() function.  You can do it with structure(), and your 
code might be a little faster, but it will be harder to read, will break 
if someone ever changes the low-level implementation of matrices, e.g. 
by replacing it with the Matrix class.

Duncan Murdoch

  
  


  


      

    

    

      
      

        


  

        

      Duncan Murdoch
    

    

      
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On 04/11/2007 7:43 AM, Mark Difford wrote:

            

      
      
      
    

        
But a matrix is a structure, so you could use structure() to create one. 
  I wouldn't normally do that, but there might be circumstances where it 
was appropriate.

Duncan Murdoch

            

      
      
      
    

        

      
      
    

            

      
      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Brian Ripley
    

    

      
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On Sun, 4 Nov 2007, Duncan Murdoch wrote:

        

            

      
      
      
    

        
For the record

A <- <some data>
dim(A) <- c(nr, rc)

is faster than either matrix() or structure(), and seems at least as easy 
to read.  matrix() has the advantage that it will replicate the data 
to the necessary length, but both will make copies that my version does 
not if you have the right length of data.

But this is only worth worrying about if you have large matrices.

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Edna Bell
    

    

      
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I was reading "S Programming" and a set of the code used structure to
set up a matrix.

I just wondered which was better and why.

        
On 11/4/07, Mark Difford <mark_difford at yahoo.co.uk> wrote:

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Gabor Grothendieck
    

    

      
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In general, you want to use as high level a construct as possible
since then the details implementing the construct can be modified
and improved without your code changing.  This is really just an
aspect of modularity.  Thus matrix would be preferred.

Actually since R allows access to the lower level details this type of
benefit is not really guaranteed but as a matter of principle I
would use other constructs than structure whenever possible.

        
On Nov 4, 2007 8:32 PM, Edna Bell <edna.bell01 at gmail.com> wrote: