From 3e0c87ad6be3279597aa607daee196762863199a Mon Sep 17 00:00:00 2001
From: Stefan Blumentrath <stefan.blumentrath@gmx.de>
Date: Mon, 15 May 2023 12:44:34 +0200
Subject: [PATCH] r.univar: print only statistics for existing zones (#2957)

* skip zones without pixels

* add test for zones with gaps
---
 raster/r.univar/stats.c                    |  4 ++
 raster/r.univar/testsuite/test_r_univar.py | 70 +++++++++++++++++++++-
 2 files changed, 73 insertions(+), 1 deletion(-)

diff --git a/raster/r.univar/stats.c b/raster/r.univar/stats.c
index 1e061471c6e..ad48786bbcf 100644
--- a/raster/r.univar/stats.c
+++ b/raster/r.univar/stats.c
@@ -116,6 +116,10 @@ int print_stats(univar_stat *stats)
         unsigned int i;
         size_t qpos_25, qpos_75, *qpos_perc;
 
+        /* stats collected for this zone? */
+        if (stats[z].size == 0)
+            continue;
+
         /* all these calculations get promoted to doubles, so any DIV0 becomes
          * nan */
         mean = stats[z].sum / stats[z].n;
diff --git a/raster/r.univar/testsuite/test_r_univar.py b/raster/r.univar/testsuite/test_r_univar.py
index 34437261408..02678c5115b 100644
--- a/raster/r.univar/testsuite/test_r_univar.py
+++ b/raster/r.univar/testsuite/test_r_univar.py
@@ -20,6 +20,7 @@ def tearDown(self):
         self.runModule("g.remove", flags="f", type="raster", name="map_a")
         self.runModule("g.remove", flags="f", type="raster", name="map_b")
         self.runModule("g.remove", flags="f", type="raster", name="zone_map")
+        self.runModule("g.remove", flags="f", type="raster", name="zone_map_with_gap")
 
     def setUp(self):
         """Create input data"""
@@ -31,7 +32,12 @@ def setUp(self):
             "r.mapcalc", expression="map_b = 200 + row() + col()", overwrite=True
         )
         self.runModule(
-            "r.mapcalc", expression="zone_map = if(row() < 20, 1,2)", overwrite=True
+            "r.mapcalc", expression="zone_map = if(row() < 20, 1, 2)", overwrite=True
+        )
+        self.runModule(
+            "r.mapcalc",
+            expression="zone_map_with_gap = if(row()> 20, 2, 9)",
+            overwrite=True,
         )
 
     def test_1(self):
@@ -382,6 +388,68 @@ def test_3_zone(self):
             sep="=",
         )
 
+    def test_zone_with_gap_in_cats(self):
+        """
+        test if gaps in categories in a map are not included in the output
+        :return:
+        """
+
+        # Output of r.univar
+        univar_string = """zone=2;
+                           n=12600
+                           null_cells=0
+                           cells=12600
+                           min=122
+                           max=380
+                           range=258
+                           mean=251
+                           mean_of_abs=251
+                           stddev=59.8595578555895
+                           variance=3583.16666666667
+                           coeff_var=23.8484294245376
+                           sum=3162600
+                           first_quartile=201
+                           median=251
+                           third_quartile=301
+                           percentile_90=331
+                           zone=9;
+                           n=3600
+                           null_cells=0
+                           cells=12600
+                           min=102
+                           max=310
+                           range=208
+                           mean=206
+                           mean_of_abs=206
+                           stddev=56.6406803160649
+                           variance=3208.16666666667
+                           coeff_var=27.4954758815849
+                           sum=741600
+                           first_quartile=156
+                           median=206
+                           third_quartile=256
+                           percentile_90=283"""
+
+        self.assertModuleKeyValue(
+            module="r.univar",
+            map=["map_a", "map_b"],
+            zones="zone_map_with_gap",
+            flags="ge",
+            reference=univar_string,
+            precision=6,
+            sep="=",
+        )
+        self.assertModuleKeyValue(
+            module="r.univar",
+            map=["map_a", "map_b"],
+            zones="zone_map_with_gap",
+            flags="ge",
+            nprocs=4,
+            reference=univar_string,
+            precision=6,
+            sep="=",
+        )
+
 
 class TestAccumulateFails(TestCase):
     def test_error_handling(self):