tests/testthat/test-graph.knn.R

In igraph: Network Analysis and Visualization

test_that("knn works", {
  set.seed(42)

  ## Some trivial ones
  g <- make_ring(10)
  expect_that(knn(g), equals(list(knn = rep(2, 10), knnk = c(NaN, 2))))

  g2 <- make_star(10)
  expect_that(knn(g2), equals(list(
    knn = c(1, rep(9, 9)),
    knnk = c(9, rep(NaN, 7), 1)
  )))

  ## A scale-free one, try to plot 'knnk'
  g3 <- simplify(sample_pa(1000, m = 5))
  r3 <- knn(g3)
  expect_that(r3$knn[43], equals(46))
  expect_that(r3$knn[1000], equals(192.4))
  expect_that(r3$knnk[100], equals(18.78))
  expect_that(length(r3$knnk), equals(359))

  ## A random graph
  g4 <- sample_gnp(1000, p = 5 / 1000)
  r4 <- knn(g4)
  expect_that(r4$knn[1000], equals(20 / 3))
  expect_that(length(r4$knnk), equals(15))
  expect_that(r4$knnk[12], equals(19 / 3))

  ## A weighted graph
  g5 <- make_star(10)
  E(g5)$weight <- seq(ecount(g5))
  r5 <- knn(g5)
  expect_that(r5, equals(structure(list(
    knn = c(1, rep(9, 9)), knnk =
      c(
        9, NaN, NaN,
        NaN, NaN, NaN, NaN, NaN,
        1
      )
  ), .Names = c(
    "knn",
    "knnk"
  ))))
})