Whenever you zoom or pan into a region and then update the dataPoints, it still retains the viewport region and it seems to work as intended. Kindly take a look at this JSFiddle for an example on the same.
If you are still facing an issue, can you kindly create JSFiddle reproducing the issue you are facing & share it with us so that we can look into the code / chart-options being used, understand the scenario better and help you resolve?
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Adithya Menon
Team CanvasJS