Added possibility for multiple ropes

Initial commit arviz-devs#448 completely rewritten.
Rope can be a list of 2 or a dict like in posteriorplot() passed to the rope argument
Argument rope_values writes ROPE values in plot when multiple ropes are given.

arviz/plots/forestplot.py

@@ -27,8 +27,9 @@ def plot_forest(
     var_names=None,
     combined=False,
     credible_interval=0.94,
-    quartiles=True,
     rope=None,
+    rope_values=True,
+    quartiles=True,
     eff_n=False,
     r_hat=False,
     colors="cycle",
@@ -37,8 +38,7 @@ def plot_forest(
     markersize=None,
     ridgeplot_alpha=None,
     ridgeplot_overlap=2,
-    rope_alpha=.5,
-    figsize=None
+    figsize=None,
 ):
     """Forest plot to compare credible intervals from a number of distributions.
 
@@ -63,11 +63,14 @@ def plot_forest(
         chains will be plotted separately.
     credible_interval : float, optional
         Credible interval to plot. Defaults to 0.94.
+    rope: tuple or dictionary of tuples
+        Lower and upper values of the Region Of Practical Equivalence. If a list with one interval only is provided, the ROPE will be displayed across the y-axis. If more than one interval is provided the
+        length of the list should match the number of variables.
+    rope_values : bool, optional
+        Flag for plotting lower and upper values of the Region Of Practical Equivalence as text
     quartiles : bool, optional
         Flag for plotting the interquartile range, in addition to the credible_interval intervals.
         Defaults to True
-    rope: tuple
-        Lower and upper values of the Region Of Practical Equivalence defined for all displayed variables
     r_hat : bool, optional
         Flag for plotting Split R-hat statistics. Requires 2 or more chains. Defaults to False
     eff_n : bool, optional
@@ -89,8 +92,6 @@ def plot_forest(
         a black outline is used.
     ridgeplot_overlap : float
         Overlap height for ridgeplots.
-    rope_alpha : float
-        Transparency for rope interval.
     figsize : tuple
         Figure size. If None it will be defined automatically.
 
@@ -140,8 +141,7 @@ def plot_forest(
     axes = np.atleast_1d(axes)
     if kind == "forestplot":
         plot_handler.forestplot(
-            credible_interval, quartiles, xt_labelsize, titlesize, linewidth,
-            markersize, axes[0], rope, rope_alpha
+            credible_interval, quartiles, xt_labelsize, titlesize, linewidth, markersize, axes[0], rope, rope_values
         )
     elif kind == "ridgeplot":
         plot_handler.ridgeplot(ridgeplot_overlap, xt_labelsize, linewidth, ridgeplot_alpha, axes[0])
@@ -246,6 +246,23 @@ def labels_and_ticks(self):
             idxs.append(sub_idxs)
         return np.concatenate(labels), np.concatenate(idxs)
 
+    def display_multiple_ropes(self, rope, ax, y, linewidth, rope_var,markersize, rope_values,xt_labelsize):
+        vals = dict(rope[rope_var][0])["rope"]
+        ax.plot(
+            vals,
+            (y+.05, y+.05),
+            lw=linewidth * 2,
+            color="C2",
+            solid_capstyle="round",
+            zorder=0,
+            alpha=0.7,
+        )
+        text_props = {"size": xt_labelsize, "horizontalalignment": "center", "color": "C2"}
+        if rope_values:
+            ax.text(vals[0], y+.08, vals[0])#, **text_props)
+            ax.text(vals[1], y+.08, vals[1])#, **text_props)
+
+
     def ridgeplot(self, mult, xt_labelsize, linewidth, alpha, ax):
         """Draw ridgeplot for each plotter.
 
@@ -281,7 +298,7 @@ def ridgeplot(self, mult, xt_labelsize, linewidth, alpha, ax):
         return ax
 
     def forestplot(
-        self, credible_interval, quartiles, xt_labelsize, titlesize, linewidth, markersize, ax, rope, rope_alpha
+        self, credible_interval, quartiles, xt_labelsize, titlesize, linewidth, markersize, ax, rope, rope_values
     ):
         """Draw forestplot for each plotter.
 
@@ -309,6 +326,7 @@ def forestplot(
         else:
             qlist = [endpoint, 50, 100 - endpoint]
 
+        label, ticks = self.labels_and_ticks()
         for plotter in self.plotters.values():
             for y, values, color in plotter.treeplot(qlist, credible_interval):
                 mid = len(values) // 2
@@ -325,11 +343,18 @@ def forestplot(
                     markersize=markersize * 0.75,
                     color=color,
                 )
-        if rope is not None and len(rope) == 2:
-            ax.axvspan(rope[0], rope[1], 0, len(values), color='C2', alpha=rope_alpha)
-        elif rope is not None:
-            raise ValueError('Argument `rope` must be None or an '
-                             'iterable of length 2')
+                if isinstance(rope, dict):
+                    self.display_multiple_ropes(rope, ax, y, linewidth, label[ticks==y][0],markersize, rope_values,xt_labelsize)
+        if rope is None or isinstance(rope, dict):
+            return
+        elif len(rope) == 2:
+            ax.axvspan(rope[0], rope[1], 0, self.y_max(), color='C2', alpha=.5)
+        else:
+            raise ValueError(
+                "Argument `rope` must be None, a dictionary like"
+                '{"var_name": {"rope": (lo, hi)}}, or an '
+                "iterable of length 2"
+            )
         ax.tick_params(labelsize=xt_labelsize)
         ax.set_title(
             "{:.1%} Credible Interval".format(credible_interval), fontsize=titlesize, wrap=True