For example, if a value is NaN then replace it with a different numeric value and plot that value.
As far as I can tell the existing ‘value mapping’ feature only modifies the hover tool tip text and does not change the data being plotted.
I was thinking of using NaN values to store temperature sensor readings that were suspect and therefore couldn’t be trusted, however I don’t see an obvious way of plotting NaNs on a graph that makes sense to a human, so I think I need a way of replacing NaNs for something that would be obvious as an error such as -100.