BF: new numpy protects polynomial coefficients

New numpy returns a copy of the polynomial coefficients from poly.c,
rather than the actual coefficent array, so when we were modifying the
polynomial coefficients, the polynomial object wasn't seeing our
changes, leading to errors in the RFT module - see e.g.

https://nipy.bic.berkeley.edu/builders/nipy-py2.7-osx-10.10/builds/52/steps/shell_9/logs/stdio

Numpy issue raised on numpy-discussion mailing list.

nipy/algorithms/statistics/rft.py

@@ -87,14 +87,14 @@ def Q(dim, dfd=np.inf):
     j = dim
     if j <= 0:
         raise ValueError('Q defined only for dim > 0')
-    poly = hermitenorm(j-1)
-    poly = np.poly1d(np.around(poly.c))
+    coeffs = np.around(hermitenorm(j - 1).c)
     if np.isfinite(m):
-        for l in range((j-1)//2+1):
-            f = np.exp(gammaln((m+1)/2.) - gammaln((m+2-j+2*l)/2.)
-                                - 0.5*(j-1-2*l)*(np.log(m/2.)))
-            poly.c[2*l] *= f
-    return np.poly1d(poly.c)
+        for L in range((j - 1) // 2 + 1):
+            f = np.exp(gammaln((m + 1) / 2.)
+                       - gammaln((m + 2 - j + 2 * L) / 2.)
+                       - 0.5 * (j - 1 - 2 * L) * (np.log(m / 2.)))
+            coeffs[2 * L] *= f
+    return np.poly1d(coeffs)
 
 
 class ECquasi(np.poly1d):

nipy/algorithms/statistics/tests/test_rft.py

@@ -400,16 +400,16 @@ def test_hotelling2():
         chi = rft.ChiSquared(dfn=dfn)(x)
         assert_almost_equal(h, chi)
         chi2 = scipy.stats.chi2.sf(x, dfn)
-        yield assert_almost_equal, h, chi2
+        assert_almost_equal(h, chi2)
         # XXX - p appears to be unused
         p = rft.spherical_search(dfn)
         for dfd in [40,50]:
             fac = (dfd-dfn+1.)/(dfd*dfn)
             h = rft.Hotelling(dfd=dfd,k=dfn)(x)
             f = scipy.stats.f.sf(x*fac, dfn, dfd-dfn+1)
             f2 = rft.FStat(dfd=dfd-dfn+1,dfn=dfn)(x*fac)
-            yield assert_almost_equal, f2, f
-            yield assert_almost_equal, h, f
+            assert_almost_equal(f2, f)
+            assert_almost_equal(h, f)
 
 
 @dec.slow