From eee4576f83f85fc6e1683a7f7b1c26d5267ba7cb Mon Sep 17 00:00:00 2001
From: Markus Utke <markusutke@gmx.de>
Date: Fri, 22 Sep 2023 14:43:13 +0200
Subject: [PATCH] added support for more edge case elections

---
 pabutools/analysis/category.py          | 4 ++++
 pabutools/analysis/profileproperties.py | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/pabutools/analysis/category.py b/pabutools/analysis/category.py
index a473e9b4..78b832ae 100644
--- a/pabutools/analysis/category.py
+++ b/pabutools/analysis/category.py
@@ -66,6 +66,10 @@ def category_proportionality(
             app_total_cost += project.cost
             for category in project.categories:
                 app_cost_per_category[category] += project.cost
+        if app_total_cost == 0:
+            raise ValueError(
+                "Category proportionality can only be computed for instances with at least one non-empty ballot."
+            )
         for category in categories:
             proportional_app_cost_per_category[category] += (
                 app_cost_per_category[category]
diff --git a/pabutools/analysis/profileproperties.py b/pabutools/analysis/profileproperties.py
index 4aafbaa7..9e029985 100644
--- a/pabutools/analysis/profileproperties.py
+++ b/pabutools/analysis/profileproperties.py
@@ -52,6 +52,8 @@ def median_ballot_length(instance: Instance, profile: AbstractProfile) -> int:
             The median length of the ballots in the profile.
 
     """
+    if profile.num_ballots() == 0:
+        return 0
     ballot_lengths = np.zeros(profile.num_ballots())
     index = 0
     for ballot in profile:
@@ -100,6 +102,8 @@ def median_ballot_cost(instance: Instance, profile: AbstractProfile) -> Number:
             The median cost of the ballots in the profile.
 
     """
+    if profile.num_ballots() == 0:
+        return 0
     ballot_costs = np.zeros(profile.num_ballots())
     index = 0
     for ballot in profile:
@@ -148,6 +152,8 @@ def median_approval_score(
             The median approval score of projects.
 
     """
+    if len(instance) == 0:
+        return 0
     return float(
         np.median([frac(profile.approval_score(project)) for project in instance])
     )
@@ -190,6 +196,8 @@ def median_total_score(instance: Instance, profile: AbstractCardinalProfile) ->
             The median score assigned to a project.
 
     """
+    if len(instance) == 0:
+        return 0
     return float(
         np.median([frac(profile.total_score(project)) for project in instance])
     )