Expands a vector of individual-varying values into a 2-d matrix of the appropriate size for use in MRA model formulas.
The vector of individual varying values to expand. This can be
a factor (see
Number of sampling occasions. Default is to use the 'ns' attribute
A vector of integers specifying which levels of a factor
to drop. Only applicable if
A 2-d matrix of size
ns suitable for passing to the
Fortran DLL of MRA for estimation. Values within rows are constant, values
across rows vary according to
x is a factor, this matrix
contains 0-1 indicator functions necessary to fit the factor.
x is a factor, attributes of the returned matrix are
"levels" = levels of the factor and "contr" = contrasts used in the coding (always
contr.treatment). For other contrast coding of factors, make your own
2-d matrix with a call to the appropriate function (like
Trent McDonald, WEST-INC, email@example.com
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nan <- 30 ns <- 5 age <- as.factor(sample( c("J","S1","S2","Adult"), size=nan, replace=TRUE )) attr(age,"ns") <- ns # Note that levels get reordered (by R default, alphabetically) attr(age,"drop.levels") <- (1:length(levels(age)))[ levels(age) == "J" ] age.mat <- ivar(age) # level J is the reference age.mat <- ivar(age, drop=4) # level S2 is the reference # Look at 3-D matrix produced when called with a factor. dim(age.mat) <- c(nan,ns,length(levels(age))-1) print(age.mat) # each page is the 2-d matrix used in the fit. print(age.mat[1,,]) age.mat <- ivar(age, drop=c(3,4)) # level S1 and S2 are combined and are the reference # compare above to ivar( c(1,1,2,2,3,3), 5 )
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