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The LOGISTIC Procedure

Computational Resources

The memory needed to fit a model is approximately 24(n+2)2 bytes, where n is the number of parameters estimated. For models with more than two response levels, a test of the parallel lines assumption requires an additional memory of approximately 4k2(m+1)2 + 24(m+2)2 bytes, where k is the number of response levels and m is the number of slope parameters. However, if this additional memory is not available, the procedure skips the test and finishes the other computations. You may need more memory if you use the SELECTION= option for model building.

The data that consist of relevant variables (including the design variables for model effects) and observations for fitting the model are stored in the utility file. If sufficient memory is available, such data will also be kept in memory; otherwise, the data are reread from the utility file for each evaluation of the likelihood function and its derivatives, with the resulting execution time of the procedure substantially increased.

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