• Have you ever seen a red line around a pie chart and not understood why it was there?

Pie Chart Problem:

Surprisingly, this red line popped up in a pie chart in one of my projects this week.

red line in pie chart

Pie Chart Solution:

This was puzzling at first.  When troubleshooting, I generally attempt to make changes or adjustments in order to generate any change in behavior that indicates the source of the problem, so I played with marking.  I changed the filtering scheme.  I changed the sector by and sector size by variable.  When I changed my sector size by variable, the red line shifted but didn’t disappear.

It turns out that the sum of the values behind the wedge are negative, and this is a problem because Spotfire pie charts will never show a negative wedge.  If you hover the mouse over a wedge with the red line, a tool tip will appear and you can see the ratio, which is difference from the sector size by variable.  The ratio will be negative.

Pie charts created with negative values will always have the red line.  Unfortunately, this is by design and can’t be turned off.  However, with that said, it’s most likely the case that the pie chart isn’t the right visualization for the data or perhaps you should consider grouping the data differently so that none of the wedges have a negative sum.

 

Written by Julie Schellberg of Big Mountain Analytics, LLC
Residing in Whitefish, MT, an analytics partner with Ruths.ai. Specializing in Spotfire analytics, dabbling in Power BI and R.