Allow title_quantiles inheritance from quantiles only if len (quantiles)==3

src/corner/core.py

@@ -71,9 +71,12 @@ def corner_impl(
     if titles is None:
         titles = labels
 
-    # deal with title quantiles so they much quantiles unless desired otherwise
+    # If title_quantiles is not supplied, provide the
+    # value from quantiles if and only len (quantiles)
+    # is 3, otherwise fall back to default [0.16, 0.5, 0.84]
+    # value
     if title_quantiles is None:
-        if len(quantiles) > 0:
+        if len(quantiles) == 3:
             title_quantiles = quantiles
         else:
             # a default for when quantiles not supplied.

src/corner/corner.py

@@ -140,13 +140,15 @@ def corner(
         uses labels as titles.
 
     show_titles : bool
-        Displays a title above each 1-D histogram showing the 0.5 quantile
-        with the upper and lower errors supplied by the quantiles argument.
+        Displays a title above each 1-D histogram showing the middle value,
+        lower and upper error as specified by the quantiles values provided
+        in `title_quantiles`.
 
     title_quantiles : iterable
         A list of 3 fractional quantiles to show as the the upper and lower
-        errors. If `None` (default), inherit the values from quantiles, unless
-        quantiles is `None`, in which case it defaults to [0.16,0.5,0.84]
+        errors. If `None` (default), and if `quantiles` has exactly three
+        element, inherit the values from `quantiles`. Otherwise, it defaults
+        to [0.16,0.5,0.84]
 
     title_fmt : string
         The format string for the quantiles given in titles. If you explicitly

tests/test_corner.py

@@ -115,12 +115,19 @@ def test_title_quantiles_default():
 )
 def test_title_quantiles_raises():
     with pytest.raises(ValueError):
-        _run_corner(quantiles=[0.05, 0.16, 0.5, 0.84, 0.95], show_titles=True)
+        _run_corner(
+            title_quantiles=[0.05, 0.16, 0.5, 0.84, 0.95], show_titles=True
+        )
 
     # This one shouldn't raise since show_titles isn't provided
     _run_corner(quantiles=[0.05, 0.16, 0.5, 0.84, 0.95])
 
 
+def test_len_quantiles():
+    # This test should not raise an error, as title_quantile should default to [0.16, 0.5, 0.84]
+    _run_corner(quantiles=[0.05, 0.16, 0.5, 0.84, 0.95], show_titles=True)
+
+
 @image_comparison(
     baseline_images=["color"], remove_text=True, extensions=["png"]
 )