I'm currently working on a tool that plots real time graphs.
Some of the metrics are ratios and sometimes the values are such that you might be trying to divide a number by zero.
The mathematically correct thing to show in this case is 'Undefined'
x/0 = undefined
What's the best way of plotting this on a graph? An what should the current value display?
Is it just best to be honest and say undefined?
I've seen other people just pretend the answer's zero, but I think that's misleading...
it'll vary by case, but blank spots with a note that some points are undefined might work. I'm not sure if this is a generalized tool or for a specific dataset, but if it's the latter, you should be able to point out why it's undefined too. Like "such and such is zero."
a very common way to show this is with the value NAN, not a number, this is good in table format, or on a graph as mentioned above include *=NAN
One other practice I use with ratio metrics: in a related graphic to your main display (either overlayed with a different scale or a different image) show the numerator and denominator series, then missing values or zero values in the denominator can be seen at a glance and provide the viewer with insight into the missing-ness (e.g. num and denom missing, denom zero and numerator zero, etc) . When ratio values have an interesting pattern, you need to know what drives the ratio so I like to have the data to answer the question at hand.
Sorry for not replying sooner!
I really like the solution of actually showing the calculation. I think it's by far the clearest. Hopefully we'll be able to fit it in the space.
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