# R/get_weights.r In plspm: Tools for Partial Least Squares Path Modeling (PLS-PM)

#' @title Outer Weights
#'
#' @details
#' Internal function. \code{get_weights} is called by \code{plspm}
#'
#' @note
#' Calculate outer weights (under Lohmoller's algorithm)
#'
#' @param X scaled data
#' @param path_matrix matrix with path connections
#' @param blocks list with variables in each block
#' @param specs list with algorithm specifications
#' @return list of outer weights, ODM, iter
#' @export
#' @template internals
#' @keywords internal
get_weights <- function(X, path_matrix, blocks, specs)
{
lvs = nrow(path_matrix)
mvs = ncol(X)
sdv = sqrt((nrow(X)-1) / nrow(X))   # std.dev factor correction
blockinds = indexify(blocks)

# outer design matrix 'ODM' and matrix of outer weights 'W'
ODM = list_to_dummy(blocks)
W = ODM %*% diag(1/(apply(X %*% ODM, 2, sd)*sdv), lvs, lvs)
w_old = rowSums(W)
iter = 1

repeat
{
# external estimation of LVs 'Y'
Y = X %*% W
Y = scale(Y) * sdv
# matrix of inner weights 'e'
E <- switch(specs\$scheme,
"centroid" = sign(cor(Y) * (path_matrix + t(path_matrix))),
"factorial" = cor(Y) * (path_matrix + t(path_matrix)),
"path" = get_path_scheme(path_matrix, Y))
# internal estimation of LVs 'Z'
Z = Y %*% E
#    Z = Z %*% diag(1/(apply(Z,2,sd)*sdv), lvs, lvs)  # scaling Z
# computing outer weights 'w'
for (j in 1:lvs)
{
if (specs\$modes[j] == "A")
W[blockinds==j,j] <- (1/nrow(X)) * Z[,j] %*% X[,blockinds==j]
if (specs\$modes[j] == "B")
W[blockinds==j,j] <- solve.qr(qr(X[,blockinds==j]), Z[,j])
}
w_new = rowSums(W)
w_dif = sum((abs(w_old) - abs(w_new))^2)
if (w_dif < specs\$tol || iter == specs\$maxiter) break
w_old = w_new
iter = iter + 1
} # end repeat

# preparing results
if (iter == specs\$maxiter) {
results = NULL
} else {
W = W %*% diag(1/(apply(X %*% W, 2, sd)*sdv), lvs, lvs)
w_new = rowSums(W)
names(w_new) = colnames(X)
dimnames(W) = list(colnames(X), rownames(path_matrix))
results = list(w = w_new, W = W, ODM = ODM, iter = iter)
}
# output
results
}

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plspm documentation built on May 2, 2019, 7:05 a.m.