The longpower package contains functions for computing
power and sample size for linear models of longitudinal data
based on the formula due to Liu and Liang (1997) and Diggle et
al (2002). Either formula is expressed in terms of marginal
model or Generalized Estimating Equations (GEE) parameters.
This package contains functions which translate pilot mixed
effect model parameters (e.g. random intercept and/or slope)
into marginal model parameters so that the formulas of Diggle
et al or Liu and Liang formula can be applied to produce sample
size calculations for two sample longitudinal designs assuming
known variance.