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context("layout_with_mds")
test_that("layout_with_mds works", {
library(igraph)
## A tree
g <- make_tree(10, 2, "undirected")
mymds <- function(g) {
sp <- distances(g)
sp <- sp * sp
sp <- sp - rowMeans(sp) - rep(rowMeans(sp), each=nrow(sp)) + mean(sp)
sp <- sp / -2
ei <- eigen(sp)
va <- sqrt(abs(ei$values[1:2]))
ei$vectors[,1:2] * rep(va, each=nrow(sp))
}
expect_that(mymds(g), equals(layout_with_mds(g)))
## plot(g, layout=ll)
## A graph with multiple components, just test that it runs
set.seed(42)
g <- make_ring(10) + make_ring(3)
expect_that(ncol(layout_with_mds(g)), equals(2))
## Small stress test
for (i in 1:10) {
g <- sample_gnp(100, 2/100)
l <- layout_with_mds(g)
expect_that(ncol(l), equals(2))
}
})
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