A good software package not only provides a broad range of graph templates, but it also allows you to interact dynamically with plotted data. The ability to perform the following actions sets a scientific graphing and data analysis software apart from others.
Analyze and edit individual data points in a graph
Interactively select, highlight, modify, or even remove data points. View the XY coordinates of a selected data point.
Select and analyze a range of data
Visually select a part of the data to work with. For example, select only a portion of the plotted data and find peaks in that region.
Zoom in and out your data
Use tools to quickly zoom in or out of a selected section of data. View the enlarged region and the full range in the same graph or in different graphs.
Links between the worksheet data and the plotted data
Maintain a "live-link" with the worksheet so that any action that changes the data in the graph is also reflected in the worksheet and vice versa.