I have a program that displays a dense collection of line series. I can select series from a tree view to the left of the chart.

My issue is I need an elegant way to show the user which line series is selected. Thicker lines dont work as they tend to get in the way of other lines. Dashed lines dont work as the the lines are so volatile you either miss out on important features of the graph, or cant tell its dashed at all.

Any other solutions?

  • Could you provide a mockup of your current state? Commented Aug 8, 2018 at 9:01

2 Answers 2


You could lower the transparency or saturation of all the other lines, to highlight the selected series or add a drop-shadow / glow to it.

  • 1
    +1 for changing the transparency or saturation (although it should be increasing the transparency / lowering the opacity).
    – user109724
    Commented Aug 8, 2018 at 20:40
  • Really like this solution, it addresses both my issues. Thanks!
    – Loocid
    Commented Aug 9, 2018 at 2:05
  • @gerstemout You're right, thanks, mixed up opacity and transparency ;)
    – Rick P
    Commented Aug 9, 2018 at 8:45

In addition to @Rick, if you have a lot of lines on the graph, it might be difficult to assess the value for a given x.

Highcharts solves this issue by making a tooltip visible whenever the mouse is moving on the line of the chart. It makes it very clear which line is concerned and the given value.

Illustration of a tooltip displayed

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