If you find yourself making the charts for your presentations in Numbers and would like an easy way to update them, the chart updating feature in Keynote does just that. With a simple click, your chart in Keynote is updated to reflect changes made in your Numbers spreadsheet.
This feature requires that you start your workflow in Numbers. After creating a chart, copy and paste it over to a slide in Keynote.
Now, whenever you click on the chart in your Keynote presentation, a button will appear atop of it.
Clicking on the arrow with the two circles on it will update the chart with figures from Numbers. Alternatively, you can click on the "edit data" button (after clicking on the chart) and then "update all" within the data table. However, it's important to note that you must save the Numbers file first before doing this. Otherwise, the changes won't carry over.