@jeppy7,
You should call chart.render() to render chart once options are set or updated. You can also use set method to achieve the same without calling chart.render() as the method re-renders chart.
chart.data[0].set("indexLabel", "{label} {y}");
.
Note: Chart should be rendered once before you can use set method
When I do that I get some weird behavior though. The circle doesn’t redraw very well, etc.
Can you kindly create jsfiddle reproducing the issue, so that we can understand it better and help you out?
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Indranil Deo,
Team CanvasJS