Adding a horizontal bar small multiples example

doc/python/facet-plots.md

@@ -54,6 +54,8 @@ fig.show()
 
 ### Bar Chart Row Facets
 
+There is a more presentation-ready horizontal, faceted bar chart in the [horizontal bar documentation](/python/horizontal-bar-charts/#Small-multiple-horizontal-bar-charts-show-each-component's-size-more-clearly-than-a-stacked-bar)
+
 ```python
 import plotly.express as px
 df = px.data.tips()

doc/python/horizontal-bar-charts.md

@@ -107,6 +107,52 @@ fig.add_trace(go.Bar(
 ))
 
 fig.update_layout(barmode='stack')
+fig.show()
+```
+### Small multiple horizontal bar charts show each component's size more clearly than a stacked bar
+
+Bar charts with multiple components pose a fundamental trade off between presenting the total clearly and presenting the component values clearly.  This small multiples approach shows the component magnitudes clearly at the cost of slightly obscuring the totals.  A stacked bar does the opposite.  Small multiple bar charts often work better in a horizontal orientation; and are easy to create with the px.bar orientation and facet_col parameters.
+
+  .
+
+```
+import pandas as pd
+import plotly.express as px
+
+data = {
+    "Quarter": ["Q1", "Q2", "Q3", "Q4"] * 3,
+    "Region": ["North", "North", "North", "North", "South", "South", "South", "South", "West", "West", "West", "West"],
+    "Outcome": [150, 200, 250, 300, 120, 180, 240, 310, 100, 150, 220, 280]
+}
+df = pd.DataFrame(data)
+
+
+fig = px.bar(
+    df, 
+    x="Outcome", 
+    y="Region",
+    orientation="h",  
+    facet_col="Quarter", 
+    title="Number of Patients Served by Region and Quarter", 
+    labels={"Outcome": "Patients Served", "Region": "Region"} 
+)
+
+## the section below is optional clean up to make this presentation ready
+
+fig.update_layout(
+    height=400,  #the Plotly default makes the bars awkwardly large; setting a height improves the display
+    showlegend=False,  # the legend does not add anything
+)
+
+#remove up the default "facet_variable =" text from the title of each facet graph
+fig.for_each_annotation(lambda a: a.update(text=a.text.split("=")[-1]))  
+
+# Remove duplicate axis labels
+fig.for_each_yaxis(lambda axis: axis.update(title=None))
+fig.for_each_xaxis(lambda axis: axis.update(title=None))
+# add the one valuable axis label back in
+fig.update_xaxes(title="Count", row=1, col=1)
+
 fig.show()
 ```
 
@@ -335,4 +381,4 @@ fig.show()
 
 ### Reference
 
-See more examples of bar charts and styling options [here](https://plotly.com/python/bar-charts/).<br> See https://plotly.com/python/reference/bar/ for more information and chart attribute options!
+See more examples of bar charts and styling options [here](https://plotly.com/python/bar-charts/).<br> See https://plotly.com/python/reference/bar/ for more information and chart attribute options!