Translations:Extension:Graph/Interactive Graph Tutorial/21/en

Having pixel position of the handler is not very good - we would much rather have a position that is meaningful to our graph, e.g. a year. Vega scales provide a useful mechanism for converting between our data (e.g. years) and the screen coordinates, and back (invert). In this step, we add "yearsScale" linear scale for values 1960..2013, mapping it to the whole width of the graph (excluding padding). We also add a new scaledHandlePosition signal that translates from the mouse X position to the meaningful value in years.