Create a linear path in the simplex by defining a direction and a step size

Usage

CoDa_path(
  comp_direc,
  comp_from,
  step_size = 0.01,
  n_steps = 100,
  add_opposite = FALSE,
  dir_from_start = FALSE
)

Arguments

comp_direc: A numeric vector, defining a direction in the simplex
comp_from: A numeric vector, an initial point in the simplex - defaults to a balanced composition, which represents the origin in the simplex
step_size: A numeric, indicting the step size
n_steps: A numeric, indicating the number of steps to be taking from comp_from
add_opposite: A logical, if TRUE steps in the opposite direction are also computed
dir_from_start: A logical, if TRUE the direction is calculated from the difference between comp_from and comp_direc

Value

A data.frame frame where each row corresponds to one compositional vector

Details

The function is very similar to CoDa_seq(). However, of drawing a line between a starting and end point it uses only a starting point and a direction.

Author

Lukas Dargel

Examples


# three steps that go from the origin towards the defined direction
comp_direc <- c(A =.4,B = .35, C= .25)
CoDa_path(comp_direc, n_steps = 3)
#>           A         B         C
#> 0 0.3333333 0.3333333 0.3333333
#> 1 0.3352914 0.3339868 0.3307219
#> 2 0.3372497 0.3346303 0.3281200
#> 3 0.3392082 0.3352641 0.3255277


# we can draw the path that is defined by this direction
comp_direc <- c(A =.4,B = .35, C= .25)
compositions::plot.acomp(CoDa_path(comp_direc,n_steps = 10))

compositions::plot.acomp(CoDa_path(comp_direc,n_steps = 100))

compositions::plot.acomp(CoDa_path(comp_direc,add_opposite = TRUE))



# using the same direction we can draw a new path that does not go through the origin
comp_direc <- c(A =.4,B = .35, C= .25)
comp_from <- c(.7,.2,.1)
compositions::plot.acomp(CoDa_path(comp_direc, comp_from,n_steps = 10))

compositions::plot.acomp(CoDa_path(comp_direc, comp_from,n_steps = 100))

compositions::plot.acomp(CoDa_path(comp_direc, comp_from,add_opposite = TRUE))



# the balanced composition does not define a direction by itself
comp_origin <- c(A = 1/3, B = 1/3, C= 1/3) # corresponds to a zero vector in real space
try(CoDa_path(comp_origin, comp_from,add_opposite = TRUE))
#> Error in CoDa_path(comp_origin, comp_from, add_opposite = TRUE) : 
#>   The simplex direction is invalid!

# with the dir_from_start option the direction is derived
# from the simplex line connecting two compositions
path_origin <- CoDa_path(
  comp_direc = comp_origin,
  comp_from = comp_from,
  add_opposite = TRUE,
  dir_from_start = TRUE,
  step_size = .1)
compositions::plot.acomp(path_origin)
compositions::plot.acomp(comp_origin, add = TRUE, col = "blue", pch = 19)
compositions::plot.acomp(comp_from, add = TRUE, col = "red", pch = 19)