Null series values will break the line when rendering, missing values will be skipped
/* data stolen from http://howmanyleft.co.uk/vehicle/jaguar_'e'_type */ var day_data = [ {"period": "2012-10-01", "licensed": 3407}, {"period": "2012-09-30", "sorned": 0}, {"period": "2012-09-29", "sorned": 618}, {"period": "2012-09-20", "licensed": 3246, "sorned": 661}, {"period": "2012-09-19", "licensed": 3257, "sorned": null}, {"period": "2012-09-18", "licensed": 3248, "other": 1000}, {"period": "2012-09-17", "sorned": 0}, {"period": "2012-09-16", "sorned": 0}, {"period": "2012-09-15", "licensed": 3201, "sorned": 656}, {"period": "2012-09-10", "licensed": 3215} ]; Morris.Line({ element: 'graph', data: day_data, xkey: 'period', ykeys: ['licensed', 'sorned', 'other'], labels: ['Licensed', 'SORN', 'Other'], /* custom label formatting with `xLabelFormat` */ xLabelFormat: function(d) { return (d.getMonth()+1)+'/'+d.getDate()+'/'+d.getFullYear(); }, /* setting `xLabels` is recommended when using xLabelFormat */ xLabels: 'day' });