2 Replies Latest reply on Nov 28, 2012 9:48 AM by Antony Hilliard

    Plot sloped reference lines / "Cone of Uncertainty"?

    Antony Hilliard

      I've got a "CUSUM" (cumulative sum) line chart that's supposed to show accumulated savings / losses (Y-axis) over time (X-axis).  The chart is part of a dashboard that allows users to filter the timestamps to "zoom in" on the chart X-axis.

       

      The chart Y-axis currently autoscales.  This is good, but brings the risk of zooming in too far and overemphasizing a very small savings/loss trend.  I'd like to enforce a dynamic minimum scale.  This might look like diagonal reference lines that show +-2% savings rates, sort of like an expanding "cone of uncertainty".  However, the reference lines must always start at the chart origin, even if the date range is changed (i.e. they have to move with the X-axis time filter).

       

      Possibilities I've been able to come up with are:

       

      • Add a dual, hidden X and Y axes to plot the two 'cone' lines. Find some way to make the left-hand side of the 'cone' always line up with the primary axis data.
      • Set the minimum Y-axis using invisible horizontal reference lines that are somehow calculated based on the left most cumulative savings data point and X-axis span (e.g. Leftmost Savings Datapoint +- ( 60 day span * $500/day ))?
      • Add diagonal grid lines, somehow?
      • Calculate a new data stream and plot it as a reference line, but somehow recalculate it whenever the date range is changed?

       

      This seems like it might be too much work ...