Matrix manipulations Re: [Maxima] Size of a matrix

> Maxima lacks some useful functions that operate on matrices. 
> Another two of them are _deleting_ rows and columns.
> ...Does this mean that a) maxima users never delete rows/cols,
> they only add cols/rows, or b) these functions are 
> present but are undocumented, or c) writing these functions 
> should be a primer finger-excersise for any maxima beginner?

The functions are present and documented.

 - Function: SUBMATRIX (m1, ..., M, n1, ...)
     creates a new matrix composed of the matrix M with rows mi
     deleted, and columns ni deleted.

 - Function: MINOR (M, i, j)
     computes the i,j minor of the matrix M.  That is, M with row i and
     column j removed.

They are also easy finger exercises for beginners (no error-checking for
simplicity):

removerow(m,r):=
  genmatrix(
     lambda([i,j],
        m[ if i>=r then i+1 else i, j ]),
     length(m)-1,
     length(m[1]));

removecol(m,c):=
  genmatrix(
     lambda([i,j],
        m[ i, if j>=c then j+1 else j ]),
     length(m),
     length(m[1])-1);