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sub-matrix block size

6 messages · Santosh, Peter Alspach, Dennis Murphy +1 more

Peter Alspach
# 
Tena koe Santosh

It is not clear to me precisely what your blocking rules are (e.g., where should matrix[4,4] go, is matrix[5:7,5:7] to be considered as a different block to matrix[8:10,8:10]).  Also, what happens if there is an isolated 1 (e.g., in location matrix[9,6])?  However, I imagine something could be achieved with judicious use of diag() and rle().

HTH ....

Peter Alspach
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Dennis Murphy
# 
Hi:

Maybe this can help get you started. Reading your data into a matrix m,

m <- structure(c(1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0,
0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0), .Dim = c(11L,
11L))

rowSums(m) + colSums(m) - 1
 [1]  2  2  1 -1  3  3  3  3  3  3 -1

The pair of 2's => a 2 x 2 block, 1 => a 1 x 1 matrix with value 1, -1
=> a 1 x 1 matrix with entry 0, a triplet of 3's => a 3 x 3 subblock,
etc. You should be able to figure out the rows and columns for each
submatrix from the indices of the vector above; the values provide an
indication of matrix size as well as position.

HTH,
Dennis
On Tue, Apr 26, 2011 at 5:13 PM, Santosh <santosh2005 at gmail.com> wrote:
David Winsemius
#
On Apr 27, 2011, at 12:07 AM, Dennis Murphy wrote:

            

      
      
      
    

        
If we are in the stage of providing potentially useful but incomplete  
ideas, this would be my notion. Use the row and col functions with "["  
to locate non-zero elements in the diagonal and subdiagonal:

Diagonal:  (My matrix was named `mm`)
 > mm[row(mm)==col(mm)]
  [1] 1 1 1 0 1 1 1 1 1 1 0
First subdiagonal:
 > mm[row(mm)==col(mm)+1]
  [1] 0 0 0 0 0 0 0 0 0 0
First superdiagonal:
 > mm[row(mm)==col(mm)-1]
  [1] 1 0 0 0 1 1 0 1 1 0

Perhaps a combination of the two? It seems as though the rowSums/ 
colSums approach might be insensitive to whether triangular blocks  
were sub or super diagonal:

 > rowSums(mm) + colSums(mm) - 1
  [1]  2  2  1 -1  3  3  3  3  3  3 -1
 > mm[1,2]<-0
 > mm[2,1]<-1
 > rowSums(mm) + colSums(mm) - 1
  [1]  2  2  1 -1  3  3  3  3  3  3 -1

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

      
      
    

        
David Winsemius, MD
West Hartford, CT

  
  


  


      

    

    

      
      

        
      

    

    
2 days later