Absorbing factor

This can be used to reduce the amount of workspace used by REML when the Fisher scoring method is used (i.e. when the METHOD option of REML is set to Fisher). It is defined by the VCOMPONENTS directive, and can be taken from either the fixed or the random model. REML uses the factor to divide the model terms into two groups; this partition is then used in calculations during the fitting process to reduce the size of the matrices that have to be inverted and stored. Use of an absorbing factor can thus save computing time and data space. However, although exactly the same model is fitted when an absorbing factor is used, standard errors are unavailable for some model terms.