Getting control over color the end-point markers in a time line plot

Question

I made a TimeLinePlot to visualise intervals. Each interval starts with a marker en end with one.

For example:

TimelinePlot[
  {{Interval[{"Mar 20, 1990", "Jul 11, 2008"}]}, 
   {Interval[{"Sep 17, 1990", "Mar 14, 2005"}]}},
  PlotMarkers -> "Filled"]

This produces

Each interval line has a different color. I want both interval Lines to start with a red bullet and finish with a blue one.

How can I do that?

Answer 1

data = {{Interval[{"Mar 20, 1990", "Jul 11, 2008"}]}, 
  {Interval[{"Sep 17, 1990", "Mar 14, 2005"}]}};

1. You can pre-process input data to replace {Interval[{a, b}]} with {Interval[{a,b}], Style[a, Red], Style[b, Blue]} and use the option Spacings as follows:

data2 = data /. { i : Interval[{a_, b_}]} :> {i, Style[a, Red], Style[b, Blue]};

TimelinePlot[data2, Spacings -> {1, 0}, PlotMarkers -> {"Filled", .02}]

2. Alternatively, you can post-process TimelinePlot output to insert the desired directives:

tlp = TimelinePlot[data, PlotMarkers -> "Filled"];

Show[tlp, 
 Graphics[Cases[tlp, 
    PointBox[x_] :> Thread[{AbsolutePointSize[10], {Red, Blue}, Point /@ x}], All]]]

3. Use data to construct graphics primitives with desired styles to be used as Epilog in TimelinePlot:

epilog = MapIndexed[Thread[{AbsolutePointSize[10], {Red, Blue}, 
     Point /@ Thread[{#, #2[[1]]}]}] &, 
  Flatten[data] /. Interval -> Map[AbsoluteTime]];

TimelinePlot[data, Epilog -> epilog]