title: Is there a way to reorder the rows and columns of matrix to create a dense corner, in R?
body: <p>I have a large matrix which comprises 1,2 and missing (coded as NA) values. The matrix has 500000 rows by 10000 columns. There are approximately 0.05% 1- or 2-values, and the remaining values are NA.</p>
  
  <p>I would like to reorder the rows and columns of the matrix so that the top left corner of the matrix comprises a relatively high number of 1s and 2s compared to the rest of the matrix. In other words, I would like to create a relatively datarich subset of the matrix, by reordering the matrix rows and columns.</p>
  
  <p>Is there an efficient method of achieving this in R, perhaps using a library? I would also be interested in solutions in Python or Java, but I would prefer to perform this in R as it is the language that's most familiar to me.</p>
  
  <p>I thought that there maybe a set of optimisation procedures that I could use as my working matrix is too large to do the reorganisation by eye.</p>
  
  <p>I have reverted a set of edits so that the question remains consistent with the current answers.</p>