There is four ways that effects can be defined in GRD. `"factor" = slope(s)` will vary the means by an amount of s for each step of the factor; `"factor" = extent(s)` will vary the means uniformly so that there is a difference of s between the first and the last factor level; `"factor" = custom(a,b,c..)` will alter each means by an amount of a for the first, b for the second, etc. Finally `"factor" = Rexpression("R code")` will apply R code to all levels of the factors, altering the base mean.
slope(s)extent(s)
custom(...)
Rexpression(str)
These internal functions are not meant to be used in isolation in any meaningful way...
the size of the effect
a sequence with the sizes of the effects
R code string