Update bar-charts.md

Author: rl-utility-man

doc/python/bar-charts.md

@@ -306,7 +306,7 @@ fig.show()
 
 ### Stacked Bar Chart from aggregating a data frame 
 
-Stacked bar charts are a powerful way to present results summarizing categories generated using the Pandas aggregate commands, which produce a wide format data set with one row for each bar component and a column for each bar, which is the transpose of the orientation of the px.bar wide data frame.  Tranposing and updating the indexes is a somewhat involved option. Here is one straightforward way to aggregate a data set into a summarized form and present the results as a stacked bar.
+Stacked bar charts are a powerful way to present results summarizing categories generated using the Pandas aggregate commands.  DF.agg() which produces a wide format data set with one row for each bar component and a column for each bar, which is the transpose of the orientation of the px.bar wide data frame.  Tranposing and updating the indexes is a somewhat involved option. Here is one straightforward way to aggregate a data set into a summarized form and present the results as a stacked bar.
 
 ```