Plotly is an open source plotting package that is more oriented toward science than Highcharts.

Study the following:

• Can we control tooltips?
• What control do we have during selection?
• In general, can monitor or have hooks into their events?
• How hard to port histograms, scatter and density?
• How hard to create a heat map to replace density?
• Do they support optimized updates and not complete redraws?

Overall we want a sense if we should go to the next step of replacing Highcharts. We need to understand how much efforts would be involved.