| replications {stats} | R Documentation |
Returns a vector or a list of the number of replicates for each term in the formula.
replications(formula, data=NULL, na.action)
formula |
a formula or a terms object or a data frame. |
data |
a data frame used to find the objects in formula. |
na.action |
function for handling missing values. Defaults to
a na.action attribute of data, then
a setting of the option na.action, or na.fail if that
is not set. |
If formula is a data frame and data is missing,
formula is used for data with the formula ~ ..
A vector or list with one entry for each term in the formula giving
the number(s) of replications for each level. If all levels are
balanced (have the same number of replications) the result is a
vector, otherwise it is a list with a component for each terms,
as a vector, matrix or array as required.
A test for balance is !is.list(replications(formula,data)).
The design was inspired by the S function of the same name described in Chambers et al. (1992).
Chambers, J. M., Freeny, A and Heiberger, R. M. (1992) Analysis of variance; designed experiments. Chapter 5 of Statistical Models in S eds J. M. Chambers and T. J. Hastie, Wadsworth & Brooks/Cole.
## From Venables and Ripley (2002) p.165.
N <- c(0,1,0,1,1,1,0,0,0,1,1,0,1,1,0,0,1,0,1,0,1,1,0,0)
P <- c(1,1,0,0,0,1,0,1,1,1,0,0,0,1,0,1,1,0,0,1,0,1,1,0)
K <- c(1,0,0,1,0,1,1,0,0,1,0,1,0,1,1,0,0,0,1,1,1,0,1,0)
yield <- c(49.5,62.8,46.8,57.0,59.8,58.5,55.5,56.0,62.8,55.8,69.5,
55.0, 62.0,48.8,45.5,44.2,52.0,51.5,49.8,48.8,57.2,59.0,53.2,56.0)
npk <- data.frame(block=gl(6,4), N=factor(N), P=factor(P),
K=factor(K), yield=yield)
replications(~ . - yield, npk)