R/utils.R

In lindbrook/cholera: Amend, Augment and Aid Analysis of John Snow's Cholera Map

index0 <- function(x) {
  stats::setNames(data.frame(t(utils::combn(length(x), 2))), c("v1", "v2"))
}

quandrantCoordinates <- function(dat, h, theta) {
  delta <- dat[2, ] - dat[1, ]

  # Pseudo-Quadrant I
  if (all(delta > 0)) {
    post.x <- dat[2, "x"] - abs(h * cos(theta))
    post.y <- dat[2, "y"] - abs(h * sin(theta))

  # Pseudo-Quadrant II
  } else if (delta[1] < 0 & delta[2] > 0) {
    post.x <- dat[2, "x"] + abs(h * cos(theta))
    post.y <- dat[2, "y"] - abs(h * sin(theta))

  # Pseudo-Quadrant III
  } else if (all(delta < 0)) {
    post.x <- dat[2, "x"] + abs(h * cos(theta))
    post.y <- dat[2, "y"] + abs(h * sin(theta))

  # Pseudo-Quadrant IV
  } else if (delta[1] > 0 & delta[2] < 0) {
    post.x <- dat[2, "x"] - abs(h * cos(theta))
    post.y <- dat[2, "y"] + abs(h * sin(theta))

  # I:IV
  } else if (delta[1] > 0 & delta[2] == 0) {
    post.x <- dat[2, "x"] - abs(h * cos(theta))
    post.y <- dat[2, "y"]

  # I:II
  } else if (delta[1] == 0 & delta[2] > 0) {
    post.x <- dat[2, "x"]
    post.y <- dat[2, "y"] - abs(h * sin(theta))

  # II:III
  } else if (delta[1] < 0 & delta[2] == 0) {
    post.x <- dat[2, "x"] + abs(h * cos(theta))
    post.y <- dat[2, "y"]

  # III:IV
  } else if (delta[1] == 0 & delta[2] < 0) {
    post.x <- dat[2, "x"]
    post.y <- dat[2, "y"] + abs(h * sin(theta))
  }

  data.frame(x = post.x, y = post.y)
}