proc_crr {BLSM}R Documentation

Procrustean corresponding positions


Given a set of starting coordinates, the function returns the Procrustean Transform of the initial points that minimizes the sum of squared positional difference from a set of reference coordinates. The (Euclidean) distances between a candidate configuration and the reference are evaluated by considering the couples of corresponding points.

The reference configuration must be centered at the origin.


proc_crr(Z, Z0)



set of initial coordinates to be transformed


set of reference coordinates centered at the origin


Set of coordinates minimizing the distance between the initial configuration and the reference one


# Create configuration and center it at the origin
pos_ref = matrix(runif(20), ncol=2)
pos_ref = t(t(pos_ref)-colMeans(pos_ref))

# Create a new configuration by adding a perturbation to the previous one
pos = pos_ref + matrix(rnorm(20, mean=1, sd=0.1), ncol=2)

# Compute the Procrustean Transform and inspect the results
proc_pos = proc_crr(pos, pos_ref)
plot(pos_ref, col="blue", pch=20, xlim=c(-1,3), ylim=c(-1,3))
points(pos, col="red", pch=20)
points(proc_pos, col="purple", pch=20)

[Package BLSM version 0.1.0 Index]