equidistantCurve: make a curve equidistant (optionally up/downsampling)

In zarquon42b/Morpho: Calculations and Visualisations Related to Geometric Morphometrics

make a curve equidistant (optionally up/downsampling)

Description

make a curve equidistant (optionally up/downsampling)

Usage

equidistantCurve(
  x,
  n = NULL,
  open = TRUE,
  subsample = 0,
  increment = 2,
  smoothit = 0,
  mesh = NULL,
  iterations = 1
)

Arguments

x	k x m matrix containing the 2D or 3D coordinates
n	integer: number of coordinates to sample. If NULL, the existing curve will be made equidistant.
open	logical: specifies whether the curve is open or closed.
subsample	integer: number of subsamples to draw from curve for interpolation. For curves with < 1000 points, no subsampling is required.
increment	integer: if > 1, the curve is estimated iteratively by incrementing the original points by this factor. The closer this value to 1, the smoother the line but possibly farther away from the control points.
smoothit	integer: smoothing iterations after each step
mesh	specify mesh to project point to
iterations	integer: how many iterations to run equidistancing.

Details

Equidistancy is reached by iteratively deforming (using TPS) a straight line with equidistantly placed points to the target using control points with the same spacing as the actual curve. To avoid singularity, the straight line containes a small amount of noise, which can (optionally) be accounted for by smoothing the line by its neighbours.

Value

matrix containing equidistantly placed points

Note

if n >> number of original points, the resulting curves can show unwanted distortions.

Examples

## Not run: 
data(nose)
x <- shortnose.lm[c(304:323),]
xsample <- equidistantCurve(x,n=50,iterations=10,increment=2)

require(rgl)
points3d(xsample,size=5)
spheres3d(x,col=2,radius=0.3,alpha=0.5)

## End(Not run)

zarquon42b/Morpho documentation built on Jan. 28, 2024, 2:11 p.m.