Larry,
1. is it different from just add empty objects as default to each dataPoint? also no need to delete it
Both are same. However empty object in a dataSeries can affect axis-range.
2. as you can see in your solution, Xaxis is changed due to this solution. why its happens?
That’s because of empty object. To avoid this you can add a dataPoint with y-value set to null. Please take a look at this updated jsfiddle.
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Vishwas R
Team CanvasJS