Remove empty histogram bins in eq_hist (#1094)

holoviz · Jun 17, 2022 · 2557fae · 2557fae
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Showing 32 changed files with 14 additions and 12 deletions.
diff --git a/datashader/tests/data/test_001_antialias_clipped.nc b/datashader/tests/data/test_001_antialias_clipped.nc
diff --git a/datashader/tests/data/test_001_antialias_clipped.png b/datashader/tests/data/test_001_antialias_clipped.png
diff --git a/datashader/tests/data/test_001_antialias_normal.nc b/datashader/tests/data/test_001_antialias_normal.nc
diff --git a/datashader/tests/data/test_001_antialias_normal.png b/datashader/tests/data/test_001_antialias_normal.png
diff --git a/datashader/tests/data/test_002_antialias_clipped.nc b/datashader/tests/data/test_002_antialias_clipped.nc
diff --git a/datashader/tests/data/test_002_antialias_clipped.png b/datashader/tests/data/test_002_antialias_clipped.png
diff --git a/datashader/tests/data/test_002_antialias_normal.nc b/datashader/tests/data/test_002_antialias_normal.nc
diff --git a/datashader/tests/data/test_002_antialias_normal.png b/datashader/tests/data/test_002_antialias_normal.png
diff --git a/datashader/tests/data/test_003_antialias_clipped.nc b/datashader/tests/data/test_003_antialias_clipped.nc
diff --git a/datashader/tests/data/test_003_antialias_clipped.png b/datashader/tests/data/test_003_antialias_clipped.png
diff --git a/datashader/tests/data/test_003_antialias_normal.nc b/datashader/tests/data/test_003_antialias_normal.nc
diff --git a/datashader/tests/data/test_003_antialias_normal.png b/datashader/tests/data/test_003_antialias_normal.png
diff --git a/datashader/tests/data/test_004_antialias_clipped.nc b/datashader/tests/data/test_004_antialias_clipped.nc
diff --git a/datashader/tests/data/test_004_antialias_clipped.png b/datashader/tests/data/test_004_antialias_clipped.png
diff --git a/datashader/tests/data/test_004_antialias_normal.nc b/datashader/tests/data/test_004_antialias_normal.nc
diff --git a/datashader/tests/data/test_004_antialias_normal.png b/datashader/tests/data/test_004_antialias_normal.png
diff --git a/datashader/tests/data/test_005_antialias_clipped.nc b/datashader/tests/data/test_005_antialias_clipped.nc
diff --git a/datashader/tests/data/test_005_antialias_clipped.png b/datashader/tests/data/test_005_antialias_clipped.png
diff --git a/datashader/tests/data/test_005_antialias_normal.nc b/datashader/tests/data/test_005_antialias_normal.nc
diff --git a/datashader/tests/data/test_005_antialias_normal.png b/datashader/tests/data/test_005_antialias_normal.png
diff --git a/datashader/tests/data/test_005_noaa_normal.nc b/datashader/tests/data/test_005_noaa_normal.nc
diff --git a/datashader/tests/data/test_005_noaa_normal.png b/datashader/tests/data/test_005_noaa_normal.png
diff --git a/datashader/tests/data/test_006_antialias_clipped.nc b/datashader/tests/data/test_006_antialias_clipped.nc
diff --git a/datashader/tests/data/test_006_antialias_clipped.png b/datashader/tests/data/test_006_antialias_clipped.png
diff --git a/datashader/tests/data/test_006_antialias_normal.nc b/datashader/tests/data/test_006_antialias_normal.nc
diff --git a/datashader/tests/data/test_006_antialias_normal.png b/datashader/tests/data/test_006_antialias_normal.png
diff --git a/datashader/tests/data/test_007_antialias_normal.nc b/datashader/tests/data/test_007_antialias_normal.nc
diff --git a/datashader/tests/data/test_007_antialias_normal.png b/datashader/tests/data/test_007_antialias_normal.png
diff --git a/datashader/tests/data/test_007_noaa_normal.nc b/datashader/tests/data/test_007_noaa_normal.nc
diff --git a/datashader/tests/data/test_007_noaa_normal.png b/datashader/tests/data/test_007_noaa_normal.png
diff --git a/datashader/tests/test_transfer_functions.py b/datashader/tests/test_transfer_functions.py
@@ -74,21 +74,18 @@ def create_dask_array_np(*args, **kwargs):
                            coords=coords, dims=dims)
              for how, v in solution_lists.items()}
 
-eq_hist_sol = {'a': np.array([[0, 4291543295, 4288846335],
-                              [4286149631, 0, 4283518207],
-                              [4280821503, 4278190335, 0]], dtype='u4'),
-               'b': np.array([[0, 4291543295, 4288846335],
-                              [4286609919, 0, 4283518207],
-                              [4281281791, 4278190335, 0]], dtype='u4')}
-eq_hist_sol['c'] = eq_hist_sol['b']
+# Same result obtained regardless of data dtype (u4, f4, f8)
+eq_hist_sol = np.array([[0, 4291543295, 4288846335],
+                        [4286149631, 0, 4283518207],
+                        [4280821503, 4278190335, 0]], dtype='u4')
 
 eq_hist_sol_rescale_discrete_levels = {
     'a': np.array([[0, 4289306879, 4287070463],
                    [4284834047, 0, 4282597631],
                    [4280361215, 4278190335, 0]], dtype='u4'),
-    'b': np.array([[0, 4291543295, 4288846335],
-                   [4286609919, 0, 4283518207],
-                   [4281281791, 4278190335, 0]], dtype='u4')}
+    'b': np.array([[0, 4289306879, 4287070207],
+                   [4284834047, 0, 4282597375],
+                   [4280361215, 4278190335, 0]], dtype='u4')}
 eq_hist_sol_rescale_discrete_levels['c'] = eq_hist_sol_rescale_discrete_levels['b']
 
 
@@ -167,7 +164,7 @@ def test_shade(agg, attr, span):
     # span option not supported with how='eq_hist'
     if span is None:
         img = tf.shade(x, cmap=cmap, how='eq_hist', rescale_discrete_levels=False)
-        sol = tf.Image(eq_hist_sol[attr], coords=coords, dims=dims)
+        sol = tf.Image(eq_hist_sol, coords=coords, dims=dims)
         assert_eq_xr(img, sol)
 
         img = tf.shade(x, cmap=cmap, how='eq_hist', rescale_discrete_levels=True)

diff --git a/datashader/transfer_functions/__init__.py b/datashader/transfer_functions/__init__.py
@@ -180,7 +180,12 @@ def eq_hist(data, mask=None, nbins=256*256):
     else:
         hist, bin_edges = np.histogram(data2, bins=nbins)
         bin_centers = (bin_edges[:-1] + bin_edges[1:]) / 2
-        discrete_levels = None
+        keep_mask = (hist > 0)
+        discrete_levels = np.count_nonzero(keep_mask)
+        if discrete_levels != len(hist):
+            # Remove empty histogram bins.
+            hist = hist[keep_mask]
+            bin_centers = bin_centers[keep_mask]
     cdf = hist.cumsum()
     cdf = cdf / float(cdf[-1])
     out = interp(data, bin_centers, cdf).reshape(data.shape)