is.connListObj: Connection List Objects

Description

Describes the makeup of a connection list object

Usage

is.connListObj(obj)

Arguments

obj: the object to be tested

Author

Holger Hoefling

Details

A connection list object can be used to specifiy which differences in fusedlasso or flsa functions are to be penalized. Here, it is assumed that the n coefficients in the model are numbered from 0 to n-1. The connection list object is a list of length n with each element corresponding to one of the coefficients. The i-th element of the list here corresponds to coefficient with number i-1. Each element of the list is a vector of integers, naming the numbers of the coefficients to which the coefficient corresponding to the current list element is linked (i.e. the difference of the two coefficients is being penalized). I.e., assume that value $j$ is a member of the list under list element $i$. Then this means that coeffient $i-1$ and coefficient $j$ are being penalized. To understand this, consider that R-lists when viewed in C-code are being numbered starting with 0, not 1 and note that all computation is being done in C-code.

Furthermore, the connection list object has class connListObj.

Also note that the vectors in the list are of type integer not numeric. An empty vector should be set to NULL.

Examples

Run this code


connList <- vector("list", 4)
y <- 1:4

class(connList) = "connListObj"
connList[[1]] = as.integer(c(1,2))
connList[[2]] = as.integer(c(0,3))
connList[[3]] = as.integer(c(3,0))
connList[[4]] = as.integer(c(2,1))
names(connList) <- as.character(0:3) ## not necessary, just for illustration

res <- flsa(y, connListObj=connList)
res2 <- flsa(matrix(y, nrow=2))

res$BeginLambda
res2$BeginLambda
flsaGetSolution(res, lambda2=c(0, 0.5, 1))
flsaGetSolution(res2, lambda2=c(0, 0.5, 1))