I came across this while implementing the Fixed Locator:
arr := {-1. 0. 1. 4. 7}.
chart := RSChart new.
chart horizontalTick locator: (RSFixedLocator new ticks: arr).
x := 0 to: 6 by: 0.1.
y := x sin.
chart addPlot: (RSLinePlot new x: x y: y).
chart show.
I came across this while implementing the Fixed Locator: