The two graphs in this example are identical except that the plotting order was reversed.

To reverse the plotting order of the data sets on a graph, click the Rotate/Flip button in the Change section of the Prism toolbar.

 

In general, to change the order of the Data Sets, go to the Data Sets on Graph tab of the Format Graph dialog.

Changing the order of the data sets on this dialog changes the left-to-right order of the data sets on the graph. It does not change the order of the legends.