tests/testthat/test-stat-projection.r

In corybrunson/ordr: A Tidyverse Extension for Ordinations and Biplots

test_that("projection segments align with main & referent data", {
  
  # toy data
  t <- seq(3)/3 * 2*pi
  d1 <- data.frame(x1 = cos(t), x2 = sin(t))
  d2 <- data.frame(x1 = cos(1), x2 = sin(1))
  # plot layers
  p <- ggplot(d1, aes(x1, x2)) + 
    geom_segment(aes(xend = 0, yend = 0)) + 
    stat_projection(referent = d2)
  layer_data(p, 1) |> 
    subset(select = c(x, y)) |> 
    as.matrix() -> m1
  layer_data(p, 2) |> 
    transform(dx = x - xend, dy = y - yend) |> 
    subset(select = c(dx, dy)) |> 
    as.matrix() -> m2
  layer_data(p, 2) |> 
    subset(select = c(xend, yend)) |> 
    lapply(diff) |> as.data.frame() |> 
    as.matrix() -> m3
  
  # projection segments begin from main data
  expect_identical(unname(m1), unname(as.matrix(d1)))
  
  # projection segments are orthogonal to referent data
  expect_equal(max(abs(as.matrix(d2) %*% t(m2))), 0, tolerance = 1e-15)
  
  # projection segments lie on a line parallel to the referent data
  scalars <- sweep(m3, 2, unlist(d2), "/") |> apply(2, diff)
  expect_equal(scalars[[1]], scalars[[2]])
  
})