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QtiPlot is a professional scientific data analysis and visualisation solution. It is meant to be a cheap alternative to proprietary and costly software such as Origin, SigmaPlot, Regressi or Igor Pro.

SciDAVis is a free application for Scientific Data Analysis and Visualization. It's an application aimed at data analysis andpublication-quality plotting. It combines a shallow learning curve andan intuitive, easy-to-use graphical user interface with powerfulfeatures such as scriptability and extensibility. Quite extensive manual can be found here: http://scidavis.sourceforge.net/help/manual/index.html

DPlot graphing software lets scientists and engineers graph, plot, analyze, and manipulate data.

Aveloy Graph is an application for graph creation / data visualization - fast, easy to use and interactive.