In some cases you might need to show bullet only at a specific data point, not all of them. Or you might need to have a different from default bullet for some points. To do this, you should first add bullet field in your data provider, for example:
var chartData = [{ "date": "2009-10-26", "value": 72, "bullet": "round", "description": "Something good happened!" }, { "date": "2009-10-27", "value": 43 }, { "date": "2009-10-30", "value": 31 }]
Next, you have to specify bulletField for your graph. As we named this field "bullet" in data provider, we set it to "bullet":
graph.bulletField = "bullet";
If you want to show some description when user rolls-over the data item, you should add description in the data provider and also set descriptionField for your graph.
AmGraph has a possibility to set different fields like alphaField, bulletSizeField, colorField, dashLengthField, etc. You can modify the look of specific data points using the same technique.
Here is a working sample of a chart with bullets and descriptions at specific points.