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Data will most commonly be compared by looking at trends instead of exact values, so I’ll focus more on comparing graphs.
Have an add graph feature?
Top-Bottom Stacking (same x-axis)
Could be stacked like an oscilloscope. Stacking the two graphs is best for comparing data over a series of time . By stacking them vertically, the x-axis times can be aligned and we do not need to be worried about different y-axis unitsas it allows us to compare trends.
It is important to have a common reference point for the graphs where a user can highlight a time and a vertical line will appear for each graph.
I think that time will be the most common x-axis so top-bottom stacking should be the default format when comparing the graphs
[image below]
Side-By-Side Stacking (Same y-axis) (Or neither axis is the same)
Side-by-side probably isn’t as useful but if we are comparing datasets where it is more difficult to compare the units (voltage at a specific time, for example), then users may prefer it.
Multi-Series (Same x and y axes)
Area graphs are really good for comparing two lines. When communicating overall trends, the difference in colours emphasizes the amount of increase/decrease. Also blocks in the difference between the different values.
Here is an example of a multi-series plot which toggles between a graph and table format.
Comparing Exact Values
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