IGOR Pro is an interactive environment for experimentation with scientific and engineering data and for the production of publication-quality graphs and page layouts. 

IGOR Pro produces journal-quality scientific graphs.
IGOR Pro handles large data sets very quickly.
IGOR Pro includes a wide range of capabilites for analysis and graphing.
IGOR Pro has special support for time-series or other evenly-spaced data.
IGOR Pro imports data in many formats, and acquires data from GPIB and the serial port.
IGOR Pro is completely programmable via a built-in programming environment, and can be extended by external code (XOPs) written in C.
IGOR Pro doesn't require any programming; most functionality is available using standard menus, dialogs, and the mouse.