Merge pull request #174 from shoyer/add-isnull

Add isnull and notnull (wrapping pandas)

Author: shoyer

doc/api.rst

@@ -209,6 +209,9 @@ Computations
    DataArray.std
    DataArray.sum
    DataArray.var
+   DataArray.isnull
+   DataArray.notnull
+
 
 Comparisons
 ~~~~~~~~~~~

test/test_data_array.py

@@ -315,6 +315,15 @@ def test_array_interface(self):
         bar = Variable(['x', 'y'], np.zeros((10, 20)))
         self.assertDataArrayEqual(self.dv, np.maximum(self.dv, bar))
 
+    def test_is_null(self):
+        x = np.random.RandomState(42).randn(5, 6)
+        x[x < 0] = np.nan
+        original = DataArray(x, [-np.arange(5), np.arange(6)], ['x', 'y'])
+        expected = DataArray(pd.isnull(x), [-np.arange(5), np.arange(6)],
+                             ['x', 'y'])
+        self.assertDataArrayIdentical(expected, original.isnull())
+        self.assertDataArrayIdentical(~expected, original.notnull())
+
     def test_math(self):
         x = self.x
         v = self.v

xray/data_array.py

@@ -791,7 +791,7 @@ def __array_wrap__(self, obj, context=None):
     def _unary_op(f):
         @functools.wraps(f)
         def func(self, *args, **kwargs):
-            return self.__array_wrap__(f(self.variable, *args, **kwargs))
+            return self.__array_wrap__(f(self.values, *args, **kwargs))
         return func
 
     def _check_indexes_compat(self, other):

xray/ops.py

@@ -1,6 +1,7 @@
 import operator
 
 import numpy as np
+import pandas as pd
 
 from .pycompat import PY3
 
@@ -19,10 +20,11 @@
 # wrapped in an Variable/DataArray
 NUMPY_UNARY_METHODS = ['astype', 'argsort', 'clip', 'conj', 'conjugate',
                        'round']
+PANDAS_UNARY_FUNCTIONS = ['isnull', 'notnull']
 # methods which remove an axis
 NUMPY_REDUCE_METHODS = ['all', 'any', 'argmax', 'argmin', 'max', 'mean', 'min',
                         'prod', 'ptp', 'std', 'sum', 'var']
-# TODO: wrap cumprod/cumsum, take, dot, argsort/sort
+# TODO: wrap cumprod/cumsum, take, dot, sort
 
 
 def _values_method_wrapper(f):
@@ -95,4 +97,6 @@ def inject_special_operations(cls, priority=50):
         setattr(cls, name, _values_method_wrapper(name))
     for name in NUMPY_UNARY_METHODS:
         setattr(cls, name, cls._unary_op(_method_wrapper(name)))
+    for name in PANDAS_UNARY_FUNCTIONS:
+        setattr(cls, name, cls._unary_op(getattr(pd, name)))
     inject_reduce_methods(cls)