A while ago I posted the following question:
https://stackoverflow.com/questions/41292433/
I got an answer on this forum here:
viewtopic.php?f=9&t=37255&p=130830#p130841
Are there any new features added in the last couple of years that would make this any easier? It's very tricky to have to calculate crossing points of a spline... I appreciate that if I don't do it then highcharts would have to... but it would be a really neat feature to have!