adding symbols to the chart to indicate data points

[DavidHine]

Dear All
We modified the chart to render the data with a spline/curve not the simple line. This works well for things that change slowly from one value to the next.
We want to have symbols on the line where there are data points. At the moment, to find a data point and pull up the tooltip, we need to pass the cursor slowly along the curve until the tooltip appears. Not easy for novice users.

Can anyone give us some guidance on showing a symbol on the line?
We'd also welcome knowing if there is a specific d3.js chart which is the base chart so that we could study its parameters and perhaps go further.
thanks
David Hine

[DavidHine]

We solved it.