BUG: Fixed piecewise function for 0d input

When `x` has more than one element the condlist `[True, False]`
is being made equivalent to `[[True, False]]`, which is correct.
However, when `x` is zero dimensional the expected condlist is
`[[True], [False]]`: this commit addresses the issue. Besides,
the documentation stated that there could be undefined values
but actually these are 0 by default: using `nan` would be desirable,
but for the moment the docs were corrected. Closes #331.

1 files changed, 12 insertions, 20 deletions

diff --git a/numpy/lib/function_base.py b/numpy/lib/function_base.py
index 8953eebd5..00bfab6ba 100644
--- a/numpy/lib/function_base.py
+++ b/numpy/lib/function_base.py
@@ -651,7 +651,7 @@ def piecewise(x, condlist, funclist, *args, **kw):
         The output is the same shape and type as x and is found by
         calling the functions in `funclist` on the appropriate portions of `x`,
         as defined by the boolean arrays in `condlist`.  Portions not covered
-        by any condition have undefined values.
+        by any condition have a default value of 0.
 
 
     See Also
@@ -693,32 +693,24 @@ def piecewise(x, condlist, funclist, *args, **kw):
     if (isscalar(condlist) or not (isinstance(condlist[0], list) or
                                    isinstance(condlist[0], ndarray))):
         condlist = [condlist]
-    condlist = [asarray(c, dtype=bool) for c in condlist]
+    condlist = array(condlist, dtype=bool)
     n = len(condlist)
-    if n == n2 - 1:  # compute the "otherwise" condition.
-        totlist = condlist[0]
-        for k in range(1, n):
-            totlist |= condlist[k]
-        condlist.append(~totlist)
-        n += 1
-    if (n != n2):
-        raise ValueError(
-            "function list and condition list must be the same")
-    zerod = False
     # This is a hack to work around problems with NumPy's
     #  handling of 0-d arrays and boolean indexing with
     #  numpy.bool_ scalars
+    zerod = False
     if x.ndim == 0:
         x = x[None]
         zerod = True
-        newcondlist = []
-        for k in range(n):
-            if condlist[k].ndim == 0:
-                condition = condlist[k][None]
-            else:
-                condition = condlist[k]
-            newcondlist.append(condition)
-        condlist = newcondlist
+        if condlist.shape[-1] != 1:
+            condlist = condlist.T
+    if n == n2 - 1:  # compute the "otherwise" condition.
+        totlist = np.logical_or.reduce(condlist, axis=0)
+        condlist = np.vstack([condlist, ~totlist])
+        n += 1
+    if (n != n2):
+        raise ValueError(
+                "function list and condition list must be the same")
 
     y = zeros(x.shape, x.dtype)
     for k in range(n):