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Projection Explorer (PEx) is a Java-based tool that can be used to create and explore visual representations of document collections, helping the user to understand their contents. In this representation, each data instance (e.g., a document) is identified as a circle on a plane. If two circles are close, the instances they represent are similar. If the circles are distant, the instances are uncorrelated.
Using this graphical representation, it is possible to identify groups of similar data instances and the frontiers between groups. Specifically for document collections, PEx makes it possible to select groups of documents and create for such groups labels to identify the topics being mainly discussed in these groups, being possible to verify the correlation between different areas of knowledge. PEx can also be used to analyze other types of multidimensional data. For that, it is only necessary to provide a way to calculate dissimilarities between the instances of data. It is freely available for educational purposes.