perp points R version

perp_points.R

## helper functions to convert degrees to radians and vice versa =============

deg_r = function(radians) {
  180 * radians / pi
}


rad_r = function(degrees) {
  degrees * pi / 180
}

## ===========================================================================
## convert delta x and delta y to direction and length (or u & v to wd & ws)
## ===========================================================================

calc_dir = function(x, y) {
  w = deg_r(atan2(y, x))
  w = ifelse(w <= 0, w + 360, w)
  dir = 90 - w
  dir = ifelse(w >= 90, dir + 360, dir)
  return(dir)
}


calc_len = function(x, y) {
  sqrt(x*x + y*y)
}


## ===========================================================================
## convert direction and length to delta x and delta y (or wd & ws to u & v)
## ===========================================================================

calc_delta_x = function(dir, len) {
  len * sin(rad_r(dir))
}

calc_delta_y = function(dir, len) {
  len * cos(rad_r(dir))
}


## ===========================================================================
## perp point calculation
## ===========================================================================

## delta x on the right side (to be added to midpoint)
perp_rx = function(dir, len) {
  right = dir + 90
  calc_delta_x(right, len)
}

## delta y on the right side (to be added to midpoint)
perp_ry = function(dir, len) {
  left = dir + 90
  calc_delta_y(left, len)
}

## delta x on the left side (to be added to midpoint)
perp_lx = function(dir, len) {
  right = dir + 270
  calc_delta_x(right, len)
}

## delta y on the left side (to be added to midpoint)
perp_ly = function(dir, len) {
  left = dir + 270
  calc_delta_y(left, len)
}

## calculate perp points
calc_perp_point_r = function(x_offset, y_offset, dist) {
  dir = calc_dir(x_offset, y_offset)
  len = calc_len(x_offset, y_offset)
  x1_offset = calc_delta_x(dir, len * 1) + perp_rx(dir, dist)
  y1_offset = calc_delta_y(dir, len * 1) + perp_ry(dir, dist)
  mat = cbind(x1_offset, y1_offset)
  colnames(mat) = NULL
  return(mat)
}

calc_perp_point_l = function(x_offset, y_offset, dist) {
  dir = calc_dir(x_offset, y_offset)
  len = calc_len(x_offset, y_offset)
  x1_offset = calc_delta_x(dir, len * 1) + perp_lx(dir, dist)
  y1_offset = calc_delta_y(dir, len * 1) + perp_ly(dir, dist)
  mat = cbind(x1_offset, y1_offset)
  colnames(mat) = NULL
  return(mat)
}