submatrix

Yields an r by c matrix, where r is the length of the list of integers rows , and c is the length of the list of integers cols . The (i,j)-th entry of the result is m_(rows_i, cols_j). If necessary, any sequences in the lists are spliced into the list.

     i1 = R = ZZ/101[a .. o]
     
     o1 = R
     
     o1 : PolynomialRing
     

     i2 = m = genericMatrix(R, a, 3, 5)
     
     o2 = | a d g j m |
          | b e h k n |
          | c f i l o |
     
                  3       5
     o2 : Matrix R  <--- R
     

     i3 = submatrix(m, {1,2,0}, {0..2, 4})
     
     o3 = | b e h n |
          | c f i o |
          | a d g m |
     
                  3       4
     o3 : Matrix R  <--- R
     

If rows or cols is omitted, all the indices are used.

     i4 = submatrix(m, {1,2}, )
     
     o4 = | b e h k n |
          | c f i l o |
     
                  2       5
     o4 : Matrix R  <--- R
     

It is an error if any element of rows or cols is out of range.

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