How to add error bars to a stacked bar chart?

Question

Sorry, I know how to make error bars on normal bar charts, but how can I add vertical error bars to the top of my stacked bar charts, please?

BarChart[{{5, 5, 5}, {5, 5, 5}}, ChartLayout -> "Stacked"]

Something that would look like this:

I managed to cheat using `Show, but I'd prefer a more elegant method.

Answer 1

Update: In versions 12.0+, you can use Around:

BarChart[{{5, Around[5, 6], 5}, {2, Around[2, 3], 4}}, 
 ChartLayout -> "Stacked"] 

Original answer:

You can use a slightly modified version of the function errorBar from howto/AddErrorBarsToChartsAndPlots (see also this Q/A):

ClearAll[errorBar]
errorBar[type_: "Rectangle"]:= Module[{error = If[#3 === {}, 0, #3[[1]]], 
   x0 = #[[1, 1]], x1 = #[[1, 2]], y1 = #[[2, 2]]},   
 {ChartElementData[type][##],  {Black, 
  Line[{{{(x0 + x1) / 2, y1 - error}, {(x0+x1)/2 ,  y1  + error}}, 
   {{1/4 (3 x0 + x1), y1 + error}, {1/4 (x0 + 3 x1),  y1  + error}}, 
   {{1/4 (3 x0 + x1), y1  - error}, {1/4 (x0 + 3 x1), y1  - error}}}]}}]&

and add the error information as metadata to the last element in each data group

BarChart[{{5, 5, 5 -> 7}, {2, 3, 4 -> 2}}, ChartLayout -> "Stacked", 
 ChartElementFunction -> {Automatic, Automatic, errorBar[]}]

Update: What if I want to put the error bar on the second rectangle out of the three?

You can post-process the BarChart output to reorder groups of primitives so that the second rectangle (and the error lines associated with it) is at the end:

bc = BarChart[{{5, 5 -> 6, 5}, {2, 3 -> 2, 4}}, 
 ChartLayout -> "Stacked", 
 ChartElementFunction -> {Automatic, errorBar[], Automatic}]; 
bc /. x : {{_Directive, __} ..} :> RotateLeft[x, 2]