Why the line graph breaks when there are 0 values instead of going down to the x axis
|Knowledge Article Number||000086457|
|Description||We have setup a number of line charts to record snapshots of product. The report for some of the summary headings show values but on the line chart there are no graphic lines to plot 0 where there is no data .|
|Resolution||Salesforce does not plot missing (null) values. If a missing value occurs in the middle of a data set, Salesforce displays a gap in the line.
Here is the existing request posted in the idea exchange website. It provides the explanation of why it doesn't plot where data is null or missing. The industry consensus is to not plot anything if there is no data.
Here is the link of the paper written by an industry leader on visualizing data.