```
library(uwot)
context("Spectral")
test_that("1 dimensional output gives a matrix", {
expect_ok_matrix(spectral_init(V_union, ndim = 1, verbose = FALSE), nc = 1)
expect_ok_matrix(normalized_laplacian_init(V_union,
ndim = 1,
verbose = FALSE
), nc = 1)
expect_ok_matrix(laplacian_eigenmap(V_union, ndim = 1, verbose = FALSE),
nc = 1
)
# 23: ndim was always 2
expect_ok_matrix(agspectral_init(V_union, n_neg_nbrs = 2, ndim = 1, verbose = FALSE),
nc = 1
)
})
test_that("connected components", {
# Example from doc of scipy.sparse.csgraph.connected_components
graph <- as(Matrix::drop0(matrix(
c(
0, 1, 1, 0, 0,
0, 0, 1, 0, 0,
0, 0, 0, 0, 0,
0, 0, 0, 0, 1,
0, 0, 0, 0, 0
),
nrow = 5, byrow = TRUE
)), "generalMatrix")
cc_res <- connected_components(graph)
expect_equal(cc_res$n_components, 2)
expect_equal(cc_res$labels, c(0, 0, 0, 1, 1))
# Slightly more complicated example validated by running the Python version
graph100 <- matrix(0, nrow = 10, ncol = 10)
graph100[cbind(c(2, 6, 7, 8), c(5, 3, 7, 6))] <- 1
graph100 <- Matrix::drop0(graph100)
g100_nc <- 7
g100_labels <- c(0, 1, 2, 3, 1, 2, 4, 2, 5, 6)
cc_res <- connected_components(graph100)
expect_equal(cc_res$n_components, g100_nc)
expect_equal(cc_res$labels, g100_labels)
# test recursive initialization of components
sgraph <- graph + Matrix::t(graph)
expect_ok_matrix(spectral_init(sgraph), nr = 5, nc = 2)
})
```

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