use get_bins function to compute bins for density and posterior plot

CHANGELOG.md

@@ -11,6 +11,8 @@
 * Add `skipna` argument to `hpd` and `summary` (#1035)
 
 ### Maintenance and fixes
+* Fixed bug in density and posterior plot bin computation (#1049)
+* Fixed bug in density plot ax argument (#1049)
 * Fixed bug in extracting prior samples for cmdstanpy (#979)
 * Fix erroneous warning in traceplot (#989)
 * Correct bfmi denominator (#991)

arviz/plots/backends/bokeh/densityplot.py

@@ -10,6 +10,7 @@
     _create_axes_grid,
     calculate_point_estimate,
     _fast_kde,
+    get_bins,
 )
 from ....stats import hpd
 from ....stats.stats_utils import histogram
@@ -159,7 +160,7 @@ def _d_helper(
 
     else:
         xmin, xmax = hpd(vec, credible_interval, multimodal=False)
-        bins = range(xmin, xmax + 2)
+        bins = get_bins(vec)
 
         _, hist, edges = histogram(vec, bins=bins)
 

arviz/plots/backends/bokeh/posteriorplot.py

@@ -15,6 +15,7 @@
     format_sig_figs,
     round_num,
     calculate_point_estimate,
+    get_bins,
 )
 from ....stats import hpd
 
@@ -245,9 +246,7 @@ def format_axes():
     else:
         if bins is None:
             if values.dtype.kind == "i":
-                xmin = values.min()
-                xmax = values.max()
-                bins = range(xmin, xmax + 2)
+                bins = get_bins(values)
             else:
                 bins = "auto"
         kwargs.setdefault("align", "left")

arviz/plots/backends/matplotlib/densityplot.py

@@ -9,6 +9,7 @@
     _create_axes_grid,
     calculate_point_estimate,
     _fast_kde,
+    get_bins,
 )
 
 
@@ -37,16 +38,20 @@ def plot_density(
     show,
 ):
     """Matplotlib densityplot."""
-    _, ax = _create_axes_grid(
-        length_plotters,
-        rows,
-        cols,
-        figsize=figsize,
-        squeeze=False,
-        backend="matplotlib",
-        backend_kwargs=backend_kwargs,
-    )
-    axis_map = {label: ax_ for label, ax_ in zip(all_labels, ax.flatten())}
+    if ax is None:
+        _, ax = _create_axes_grid(
+            length_plotters,
+            rows,
+            cols,
+            figsize=figsize,
+            squeeze=False,
+            backend="matplotlib",
+            backend_kwargs=backend_kwargs,
+        )
+    else:
+        ax = np.atleast_2d(ax)
+
+    axis_map = {label: ax_ for label, ax_ in zip(all_labels, np.ravel(ax))}
 
     for m_idx, plotters in enumerate(to_plot):
         for var_name, selection, values in plotters:
@@ -150,7 +155,7 @@ def _d_helper(
 
     else:
         xmin, xmax = hpd(vec, credible_interval, multimodal=False)
-        bins = range(xmin, xmax + 2)
+        bins = get_bins(vec)
         if outline:
             ax.hist(vec, bins=bins, color=color, histtype="step", align="left")
         if shade:

arviz/plots/backends/matplotlib/posteriorplot.py

@@ -13,6 +13,7 @@
     format_sig_figs,
     round_num,
     calculate_point_estimate,
+    get_bins,
 )
 
 
@@ -258,7 +259,7 @@ def format_axes():
             if values.dtype.kind == "i":
                 xmin = values.min()
                 xmax = values.max()
-                bins = range(xmin, xmax + 2)
+                bins = get_bins(values)
                 ax.set_xlim(xmin - 0.5, xmax + 0.5)
             else:
                 bins = "auto"