of the programs, including Easyreg, Epidata and Instat, do not appear to handle missing data or do not handle it well. While EpiInfo has many statistical procedures, correlation is not one of them. Rather correlation is found by regression. This means that EpiInfo will not produce a single table showing correlations among multiple variables. According to the Zelig installation manual, use of Zelig requires that R and several of its libraries already be installed, and the installation also requires some degree of background in R. One limit of MicrOsiris is in handling the output. When calculations are complete, the output pages through the results, but various menu boxes also appear over the results, and so the results cannot be accessed. The output can be saved, though, as a text file and then used. One limitation is specific to programs that were developed by individuals. Support for these programs is limited to the time that the author has available. While the authors may, and often do, respond fairly quickly when there are few people asking questions, if too many people ask questions or the author is otherwise busy, support would correspondingly be slower. R is both written by and used by a large number of people all over the world, and many forums and other internet facilities can be used to get support from other users. While R is powerful, the learning curve can be rather steep for those not already familiar with other kinds of scientific programming. See also List of statistical software Journal of Statistical Software References