X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=mjo%2Fcone%2Fdoubly_nonnegative.py;h=1fb350cb46559a55b982ee3de15678e02d5a04de;hb=b760d6ffe2554def684bf1118fff22072b8cf781;hp=43a2f61c5e3fa858098175e8c9e37c08acc11e45;hpb=8698debba196d8746c1a32d8e6866085b6cb2161;p=sage.d.git

diff --git a/mjo/cone/doubly_nonnegative.py b/mjo/cone/doubly_nonnegative.py
index 43a2f61..1fb350c 100644
--- a/mjo/cone/doubly_nonnegative.py
+++ b/mjo/cone/doubly_nonnegative.py
@@ -1,4 +1,4 @@
-"""
+r"""
 The doubly-nonnegative cone in `S^{n}` is the set of all such matrices
 that both,
 
@@ -68,7 +68,7 @@ def is_doubly_nonnegative(A):
 
 
 def is_admissible_extreme_rank(r, n):
-    """
+    r"""
     The extreme matrices of the doubly-nonnegative cone have some
     restrictions on their ranks. This function checks to see whether the
     rank ``r`` would be an admissible rank for an ``n``-by-``n`` matrix.
@@ -530,7 +530,7 @@ def random_extreme_doubly_nonnegative(V, accept_zero=True, rank=None):
 
     """
 
-    if not is_admissible_extreme_rank(rank, V.dimension()):
+    if rank is not None and not is_admissible_extreme_rank(rank, V.dimension()):
         msg = 'Rank %d not possible in dimension %d.'
         raise ValueError(msg % (rank, V.dimension()))