Python's matplotlib is the best plotting solution if you want to render graphs. No other software comes even close in feature completeness and good design of the resulting images.
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Pro Multiple interactive windowing toolkits and non-interactive backends are supported
Interactive mode supports GTK, Tkinter, Qt, and wxWindows and non-interactive mode supports PDF, postscript, SVG, antigrain geometry, and Cairo backends.
Pro Syntax familiar to Matlab users
Matplotlib includes an object oriented interface as well as a Matlab-inspired functional interface.