A Line chart (or Bar or Scatter) which has the X aaxis part way up the scale (instead of the center) is not supported by default. But by using the X/Y axis drawing API objects you can achieve the same effect. The method is quite involved however and not straightforward. It involves two Y axis objects - the upper and the lower axes, an X axis object and a Line chart with chart.outofbounds set to true (and the background grid and axes disabled). The background grid here is manually drawn
` As this demo is a lot of code - you might find it easier to "build your page around the chart" instead of trying to incorporate the chart into your page.
Note: This demo differs from the other quarter axis demo in that the upper and lower halves are coloured differently - in this case in order to show positive and negative temperatures.