Add documentation about where

Author: martinRenou

docs/source/xarray.rst

@@ -126,6 +126,7 @@ where ``condition`` is falsy, and it does not evaluate ``b`` where ``condition``
 |            Python 3 - xarray                  |                C++ 14 - xframe                |
 +===============================================+===============================================+
 | ``xr.where(a > 5, a, b)``                     | ``xf::where(a > 5, a, b)``                    |
+| ``xr.where(a > 5, 100, a)``                   | ``xf::where(a > 5, 100, a)``                  |
 +-----------------------------------------------+-----------------------------------------------+
 | ``np.any(a)``                                 | ``xf::any(a)``                                |
 +-----------------------------------------------+-----------------------------------------------+
@@ -251,4 +252,3 @@ xframe universal functions are provided for a large set number of mathematical f
 +-----------------------------------------------+-----------------------------------------------+
 | ``scipy.special.gammaln(a)``                  | ``xf::lgamma(a)``                             |
 +-----------------------------------------------+-----------------------------------------------+
-