How to highlight a point on a Simple Line Chart in NVD3?

问题

I have a Simple Line Chart in NVD3 like this one http://nvd3.org/examples/line.html

I would like to highlight (overlapping a circle for example) one particular point (a given x) on my serie.

I haven't found something similar to the Highcharts addPoint() in NVD3, example: http://api.highcharts.com/highcharts#Series

Moving the tooltip programmatically could work as well.

Thanks in advance!

来源：https://stackoverflow.com/questions/27096252/how-to-highlight-a-point-on-a-simple-line-chart-in-nvd3