Excel makes an incorrect decision when graphing stacked line charts. To see why, see the first chart. This shows a stacked bar of 4 categories over time. Simple insights:
- blue appears first
- then purple shows up
- at the end, blue falls away while yellow and teal show up
One problem with this graph type is if you are showing a histogram with many data points (say weekly over several years), the bars start to clutter the area and the graph starts to look ugly, for example:
A stacked line would be much better.... so let's just change the graph type to stacked line.
What's wrong with the below?
This is the same data, yet Teal appears to be the dominating trend, even though in reality it doesn't show up until point 13. This is because Excel orders the stacked lines in the order they appear. In other words, behind the teal line is a blue line, a pink line, and a yellow line for different lengths. There is no way to reverse the appearance order (ie no "Order ->Send to Back" for data series). If you reverse the order of the series themselves, the result is this:
Fundamentally you want Blue on the bottom, followed by Pink, Yellow, then blue. The stack order conceptually should be by appearance, size, and/or causation.
This is either a mistake, or a conscious design error.
Excel Data File
