Contrasts for orthogonal Fractional Factorial 2-level designs
Contrasts for orthogonal Fractional Factorial 2-level designs
contr.FrF2(n, contrasts=TRUE)
n |
power of 2; number of levels of the factor for which contrasts are to be generated |
contrasts |
must always be |
This function mainly supports -1/+1 contrasts for 2-level factors.
It does also work if the number of levels is a power of 2.
For more than four levels, the levels of the factor must be in an appropriate order
in order to guarantee that the columns of the model matrix for an FrF2-derived structure
are orthogonal.
The function returns orthogonal contrasts for factors with number of levels a power of 2.
All contrast columns consist of -1 and +1 entries (half of each).
If factors in orthogonal arrays
with 2-level factors are assigned these contrasts, the columns of the model matrix
for the main effects model are orthogonal to each other and to the column for the intercept.
This package is currently under intensive development. Substantial changes are to be expected in the near future.
Ulrike Groemping
See Also contrasts, FrF2,
fac.design, oa.design, pb
## assign contr.FrF2 contrasts to a factor
status <- as.factor(rep(c("current","new"),4))
contrasts(status) <- contr.FrF2(2)
contrasts(status)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.