Simulate Kersplat gene means
Details
Gene means are simulated in one of two ways depending on the value of the
mean.method parameter.
If mean.method is "fit" (default) then means are sampled from a Gamma
distribution with shape equals mean.shape and rate equals
mean.rate. Expression outliers are then added by replacing some
values with the median multiplied by a factor from a log-normal distribution.
This is the same process used for the Splat simulation.
If mean.method is "density" then means are sampled from the
density object in the mean.density parameter using a rejection
sampling method. This approach is more flexible but may violate some
statistical assumptions.