Do you just wish to view this ROI or do you want to extract a subset of the data for further processing? If it's just for viewing purposes, you can off course use the zoom tool on the existing graph. If it's for viewing only and you want a second graph, use a property node to first set the active cursor and then Cursor Position:Cursor X and Cursor Position:Cursor Y. When you have x and y from both cursors, you can write this to a property node for the second graph. Autoscale has to be turned off and then you can write to Xscale:Range:Minimum, Xscale:Range:Maximum, YScale:Range:Minimum, and Yscale:Range:Maximum. If you actually want to extract a subset of the data and display it, You can again get Cursor Position:Cursor X from both cursors. This data can be used with the Array Subset function on each of the arrays. The minimum cursor value is the start index and the max value minus the min value is the length. I've attached an example that shows the last technique.
