Return NaNs as default in root widths

sleap_roots/bases.py

@@ -245,23 +245,22 @@ def get_root_widths(
 
     Returns:
         - If `return_inds` is False (default):
-            Returns an array of distances between the bases of matched roots. An empty
-            array is returned if no matching indices are found.
+            Returns an array of distances between the bases of matched roots. If no
+            matched indices are found, NaN is returned.
 
         - If `return_inds` is True:
             Returns a tuple containing the following four elements:
-                - matched_dists: Distances between the bases of matched roots. An empty
-                    array is returned if no matched indices
-                    are found.
+                - matched_dists: Distances between the bases of matched roots. If no
+                    matched indices are found, NaN is returned.
                 - matched_indices: List of tuples, each containing the indices
                     of matched roots on the left and right sides. A list containing a
                     tuple of NaNs is returned if no matched indices are found.
                 - left_bases_final: (n, 2) array containing the (x, y)
-                    coordinates of the left bases of the matched roots. An empty array
-                    of shape (0, 2) is returned if no matched indices are found.
+                    coordinates of the left bases of the matched roots. An array of
+                    NaNs is returned if no matched indices are found.
                 - right_bases_final: (n, 2) array containing the (x, y)
-                    coordinates of the right bases of the matched roots. An empty array
-                    of shape (0, 2) is returned if no matched indices are found.
+                    coordinates of the right bases of the matched roots. An array of
+                    NaNs is returned if no matched indices are found.
     """
     # Validate tolerance
     if tolerance <= 0:
@@ -275,11 +274,11 @@ def get_root_widths(
     if primary_max_length_pts.shape[1] != 2 or lateral_pts.shape[2] != 2:
         raise ValueError("The last dimension should contain x and y coordinates")
 
-    # Initialize default return values with shapes that match the expected output
-    default_dists = np.full((0,), np.nan)  # Array filled with NaN values
-    default_indices = [(np.nan, np.nan)]
-    default_left_bases = np.full((0, 2), np.nan)  # 2D array filled with NaN values
-    default_right_bases = np.full((0, 2), np.nan)  # 2D array filled with NaN values
+    # Initialize default return values
+    default_dists = np.nan
+    default_indices = [(np.nan, np.nan)]  # List of tuples with NaN values
+    default_left_bases = np.full((1, 2), np.nan)  # 2D array filled with NaN values
+    default_right_bases = np.full((1, 2), np.nan)  # 2D array filled with NaN values
 
     # Check for minimum length, or all NaNs in arrays
     if (