Modify chart data in Keynote on iPad
You can modify a chart’s data references (numbers, dates or durations) at any time. You can add and remove entire data series, or edit a data series by adding or deleting specific data from it.
Add or delete a data series
Tap the chart, then tap Edit Data.
Do any of the following:
Add a data series: Tap cells, then enter the data for your new data series.
Remove a data series: Tap the coloured bar for the row or column you want to delete, then tap Delete.
Reorder data series: Drag the coloured 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 to return to the chart.
Switch rows and columns as data series
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 the chart, then tap Edit Data.
Tap
, then tap Plot Rows as Series or Plot Columns as Series.Tap Done to return to the chart.
Share the x-axis for multiple values along the y-axis for scatter and bubble charts
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 between multiple sets of y-axis values in some types of chart.
Tap the chart to select it, then tap Edit Data.
Tap
, then tap Share X Values.Tap Done to return to the chart.
About chart downsampling
If a column, bar, line or area chart references a table with a large number of data points, the chart automatically shows a representative sample of each series to improve the performance of Keynote. Downsampling doesn’t change or remove the data in your table, and only changes the visible data points in the chart.
If your chart data is being downsampled, a message appears when you tap Large Data Set in the Chart tab of the Format 
menu.
If you want to see certain data points in your chart, you need to create the chart from a smaller table or a smaller selection of data from a large table.