Q:

highcharts line for one point serie

When having a graph with one serie and that serie has one point, the point is centered to the graph. When I have a sparkline the point is almost invisible. So were I am looking for, is a dotted or dashed line to the centered point, without a x-value. See picture

A:

You could: add a dummy point before the original data point in series data, set xAxis min to a value of the real point and set dashStyle of your series.
Example: http://jsfiddle.net/dfe9cj4u/

