[Update]
We have just released v1.9.5 Beta which supports Secondary X Axis and Multiple X / Y Axis. Please refer to the release blog for more information.
You can actually show negative values. If any of the given values are negative, y-axis/x-axis will automatically adjust. Labels are always shown at the bottom of chart area so that dataPoints don’t hide them. As of now there is no way to move the same to the center.
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Sunil