Question

Is it possible to specify a position in terms of Scaled coordinates in one direction and use the ordinary coordinates from my data points in the other direction on the plot? In other words, I want to specify a position, where the x coordinate is an ordinary coordinate and will change position in the plot if the plot range is changed, but the y coordinate is Scaled coordinate and will remain at a fixed height relative to the plot.

Answer 1

It is a bit late in coming, but is this what you are looking for?

data = {{1, 0.5}, {2, 0.7}, {3, 0.4}, {4, 0.2}};
Graphics[
  Line[data /. {x_, y_} :> Scaled[{0, y}, {x, 0}]],
  Axes -> True,
  PlotRange -> {Automatic, {0, 100}},
  AspectRatio -> Full
]