[REF] Suppresses divide by 0 warning (#786)

* Suppresses divide by 0 warning

* Adds warning on zero-counts

* Reformat

* Update warning message

* Address more review

* Fix accidental overindent

* Actually address the review maybe; finish coffee

* Switches to correct warning filter

* Add nan -> 0

* Style fixes

* Ugh style again

* Reformats again

tedana/utils.py

@@ -3,6 +3,7 @@
 """
 import logging
 import os.path as op
+import warnings
 
 import nibabel as nib
 import numpy as np
@@ -178,11 +179,22 @@ def dice(arr1, arr2, axis=None):
         raise ValueError("Axis provided {} not supported by the input arrays.".format(axis))
 
     arr_sum = arr1.sum(axis=axis) + arr2.sum(axis=axis)
-    if np.all(arr_sum == 0):
-        dsi = np.zeros(arr_sum.shape)
-    else:
-        intersection = np.logical_and(arr1, arr2)
+    intersection = np.logical_and(arr1, arr2)
+    # Count number of zero-elements in the denominator and report
+    total_zeros = np.count_nonzero(arr_sum == 0)
+    if total_zeros > 0:
+        LGR.warning(
+            f"{total_zeros} of {arr_sum.size} components have empty maps, resulting in Dice "
+            "values of 0. "
+            "Please check your component table for dice columns with 0-values."
+        )
+
+    with warnings.catch_warnings():
+        warnings.filterwarnings(
+            "ignore", category=RuntimeWarning, message="invalid value encountered in true_divide"
+        )
         dsi = (2.0 * intersection.sum(axis=axis)) / arr_sum
+    dsi = np.nan_to_num(dsi)
 
     return dsi