Gibbs sampling of U and V

A Gibbs sampler for updating the multiplicative effect matrices U and V in the symmetric case. In this case U%*%t(V) is symmetric, so this is parameterized as V=U%*%L where L is the diagonal matrix of eigenvalues of U%*%t(V).

Usage

rUV_sym_fc(E, U, V, s2 = 1, shrink=TRUE)

Arguments

E

square residual relational matrix

U

current value of U

V

current value of V

s2

dyadic variance

shrink

adaptively shrink the factors with a hierarchical prior

Value

U

a new value of U

V

a new value of V

Author

Peter Hoff

Examples

U0<-matrix(rnorm(30,2),30,2) ; V0<-U0%*%diag(c(3,-2)) 
E<- U0%*%t(V0) + matrix(rnorm(30^2),30,30) 
rUV_sym_fc 
#> function (E, U, V, s2 = 1, shrink = TRUE) 
#> {
#>     R <- ncol(U)
#>     n <- nrow(U)
#>     L <- diag((V[1, ]/U[1, ]), nrow = R)
#>     L[is.na(L)] <- 1
#>     if (shrink) {
#>         ivU <- diag(rgamma(R, (2 + n)/2, (1 + apply(U^2, 2, sum))/2), 
#>             nrow = R)
#>     }
#>     if (!shrink) {
#>         ivU <- diag(1/n, nrow = R)
#>     }
#>     for (i in rep(sample(1:n), 4)) {
#>         l <- L %*% (apply(U * E[i, ], 2, sum) - U[i, ] * E[i, 
#>             i])/s2
#>         iQ <- solve((ivU + L %*% (crossprod(U) - U[i, ] %*% t(U[i, 
#>             ])) %*% L/s2))
#>         U[i, ] <- iQ %*% l + t(chol(iQ)) %*% rnorm(R)
#>     }
#>     for (r in 1:R) {
#>         Er <- E - U[, -r, drop = FALSE] %*% L[-r, -r, drop = FALSE] %*% 
#>             t(U[, -r, drop = FALSE])
#>         l <- sum((Er * (U[, r] %*% t(U[, r])))[upper.tri(Er)])/s2
#>         iq <- 1/(1 + sum(((U[, r] %*% t(U[, r]))^2)[upper.tri(Er)])/s2)
#>         L[r, r] <- rnorm(1, iq * l, sqrt(iq))
#>     }
#>     list(U = U, V = U %*% L)
#> }
#> <bytecode: 0x560bfb8e1b28>
#> <environment: namespace:lame>