FIX: fixing floating point errors causing nan's at tile edges when th…

…e request *nearly* matches the source coordinates (up to floating point error)

podpac/core/interpolation/nearest_neighbor_interpolator.py

@@ -404,7 +404,11 @@ def select_coordinates(self, udims, source_coordinates, eval_coordinates, index_
                 if src_coords.size == 1:
                     c = src_coords.copy()
                 else:
-                    c = UniformCoordinates1d(src_start, src_stop, ndelta * src_delta, **src_coords.properties)
+                    c = UniformCoordinates1d(
+                        src_start,
+                        src_stop + ndelta * src_delta / 2,  # The delta/2 ensures the endpoint is included
+                        ndelta * src_delta,
+                        **src_coords.properties)
 
                 if isinstance(idx, slice):
                     idx = slice(idx.start, idx.stop, int(ndelta))

podpac/core/interpolation/selector.py

@@ -139,11 +139,21 @@ def _select_uniform(self, source, request, index_type):
             return np.arange(source.size)
 
         index = (crds.coordinates - source.start) / source.step
-        stop_ind = int(np.round((source.stop - source.start) / source.step))
+        stop_ind = source.size - 1
         if len(self.method) > 1:
             flr_ceil = {-1: np.floor(index), 1: np.ceil(index)}
         else:
-            flr_ceil = {0: np.round(index)}
+            # In this case, floating point error really matters, so we have to do a test
+            up = np.round(index - 1e-6)
+            down = np.round(index + 1e-6)
+            # When up and down do not agree, use the index that will be kept.
+            index_mid = down  # arbitrarily default to down when both satisfy criteria
+            Iup = up != down
+            Iup[Iup] = (up[Iup] >= 0) & (up[Iup] <= stop_ind) & ((up[Iup] > down.max()) | (up[Iup] < down.min()))
+            index_mid[Iup] = up[Iup]
+            flr_ceil = {0: index_mid}
+            # flr_ceil = {0: index}
+
         inds = []
         for m in self.method:
             sign = np.sign(m)