You can modify a chart’s data references in the chart data editor. You can enter only numbers, dates, or durations in data cells.
Tap a chart, then tap Edit Data.
Do any of the following:
Add a data series: Tap a cell, then enter your data.
Delete a data series: Tap the colored bar for the row or column you want to delete, then tap Delete.
Reorder data series: Drag the colored bar for the data series you want to move.
Enter dates, times, and durations: Tap 
, turn on Full Keyboard, then enter your data.
Tap Done.
When you add a chart, Keynote defines default data series for it. In most cases, if a table is square or if it’s wider than it is tall, the table rows are the default series. Otherwise, the columns are the default series. You can change whether rows or columns are the data series.
Tap a chart, then tap Edit Data.
Tap , then tap Plot Rows as Series or Plot Columns as Series.
Tap Done to return to the chart.
Sharing the x-axis means plotting a single kind of value along the x-axis, while allowing for multiple kinds of values plotted along the y-axis. By default, the x-axis values are shared among multiple sets of y-axis values in some types of charts.
Tap the chart, then tap Edit Data.
Tap , then tap Share X Values.
Tap Done.