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context("constraint")
test_that("constraint works", {
library(igraph)
constraint.orig <- function(graph, nodes=V(graph), attr=NULL) {
if (!is_igraph(graph)) {
stop("Not a graph object")
}
idx <- degree(graph) != 0
A <- as_adj(graph, attr=attr, sparse=FALSE)
A <- A[idx, idx]
n <- sum(idx)
one <- c(rep(1,n))
CZ <- A + t(A)
cs <- CZ %*% one # degree of vertices
ics <- 1/cs
CS <- ics %*% t(one) # 1/degree of vertices
P <- CZ * CS #intermediate result: proportionate tie strengths
PSQ <- P%*%P #sum paths of length two
P.bi <- as.numeric(P>0) #exclude paths to non-contacts (& reflexive):
PC <- (P + (PSQ*P.bi))^2 #dyadic constraint
ci <- PC %*% one #overall constraint
dim(ci) <- NULL
ci2 <- numeric(vcount(graph))
ci2[idx] <- ci
ci2[!idx] <- NaN
ci2[nodes]
}
karate <- make_graph("Zachary")
c1 <- constraint(karate)
c2 <- constraint.orig(karate)
expect_that(c1, equals(c2))
set.seed(42)
E(karate)$weight <- sample(1:10, replace=TRUE, ecount(karate))
wc1 <- constraint(karate)
wc2 <- constraint.orig(karate, attr="weight")
expect_that(wc1, equals(wc2))
})
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