Calculate the apex and base angles of an object — poly_apex_base

This function calculates the apex and base angles of an object. It takes as input a matrix of coordinates and returns the apex angle, base angle, and the coordinates of the apex and base as a list. The angles are computed after the object is aligned in the vertical axis with poly_align().

Usage

poly_apex_base_angle(
  x,
  percentiles = c(0.25, 0.75),
  invert = FALSE,
  plot = TRUE
)

Arguments

x: A matrix of coordinates representing the contour of the object, often obtained with object_contour().
percentiles: A numeric vector of two percentiles between 0 and 1 indicating the height of the points from the top to the bottom. The function calculates the apex angle between the two percentiles and the base angle between the lowest point and the highest point.
invert: If TRUE, aligns the object along the horizontal axis.
plot: Plots the polygon with the points? Defaults to TRUE.

Value

A list containing the apex angle, base angle, apex coordinates, and base coordinates.

Examples

library(pliman)
# a matrix of coordinates
angls <- poly_apex_base_angle(contours[[2]])

angls
#> $apex_angle
#> [1] 44.96998
#> 
#> $base_angle
#> [1] 57.70275
#> 
#> $apex_coords
#>             [,1]      [,2]
#> apex   -28.26853 -137.8909
#> left  -158.48484 -460.1093
#> right  108.09502 -459.6874
#> 
#> $base_coords
#>              [,1]      [,2]
#> base    -5.980237 -1426.272
#> left  -194.774675 -1104.431
#> right  160.035021 -1104.714
#> 

# or a list of coordinates
poly_apex_base_angle(contours)
#>   id apex_angle base_angle
#> 1  1   58.37192   32.28509
#> 2  2   44.96998   57.70275
#> 3  3   57.83157   41.66856
#> 4  4   44.06891   43.39274
#> 5  5   38.57844   41.63098
#> 6  6   43.34263   44.18222