QCA is based on set relations between a number of (explaining) conditions and an (explained) outcome, with the two concepts of necessity and sufficiency at its core. If some condition or combination of conditions is a superset of the outcome, the former is necessary for the latter. If some condition or combination of conditions is a subset of the outcome, the former is sufficient for the latter.
Three related variants of QCA exist: crisp-set QCA (csQCA), multi-value QCA (mvQCA) and fuzzy-set QCA (fsQCA). A subvariant of csQCA called temporal QCA (tQCA) is suitable for event sequence relations.
In this package, the "exact" Quine-McCluskey algorithm for crisp sets is implemented for csQCA and mvQCA (from version 0.6-0), and fsQCA as well as tQCA from version 1.0-0. Starting with version 0.4-5 the package has a new function called "eqmcc" ("e"nhanced Quine-McCluskey) which finds exact solutions faster and with substantially lower memory consumption (Dusa 2007, 2010).
How to make the most of R's and the QCA package's capabilities for QCA is demonstrated in detail with many examples by Thiem and Dusa (2012).
A. Dusa. A Mathematical Approach to the Boolean Minimization Problem. Quality & Quantity, 44(1): 99-113, 2010.
C. C. Ragin. The Comparative Method: Moving beyond Qualitative and Quantitative Strategies. University of California Press, Berkeley, 1987.
C. C. Ragin. Fuzzy-Set Social Science, University of Chicago Press, Chicago, 2000.
C. C. Ragin. Redesigning Social Inquiry: Fuzzy Sets and Beyond. University of Chicago Press, Chicago, 2008.
A. Thiem and A. Dusa. Qualitative Comparative Analysis with R: A User's Guide. Springer, New York, 2012.