[Solved]-Cannot read property 'cum' of undefined -- when creating a stacked area chart with xAxis.type=datetime-Highcharts

If you want to specify x coordinate for every point, use the following format of "data" :

An array of arrays with two values Example ... data: [[5, 2], [6, 3], [8, 2]]

In your case, instead of doing

data:[1,2,3,4,5].map(function(d,i) { return {x:new Date(2013,i,1),y:d*d  })

do this

data:[1,2,3,4,5].map(function(d,i) { return [new Date(2013,i,1),d*d  ]; })

Fiddle : http://jsfiddle.net/bU2Ej/1/