Get group polarization

Computes the elongation of the group at each time step t as well as the long axis vector. The elongation is a measure of how "line-link" vs "circle-like" the group is, ranging from 0 (completely circular) to 1 (completely elongated) The elongation is defined by first performing a PCA on the x/y data of the group. The axis of greatest variation is defined as the 'long axis' and the axis perpendicular to this is defined as the 'short axis'. The elonation is then defined as 1 - (length of short axis / length of long axis).

Usage

get_group_elongation(xs, ys, min_inds_tracked = 3)

Arguments

xs

N x n_times matrix giving x coordinates of each individual over time

ys

N x n_times matrix giving y coordinates of each individual over time

min_inds_tracked

if specified, sets a minimum number of individuals that must be tracked at any moment in time to compute elongation (otherwise the elongation will be NA at that time point). Default is 3 (below this, elongation is generally undefined)

Value

Returns a list containing: out$elongation: a vector of length n_times giving the elongation of the group over time out$long_axis_angle: a vector of length n_times giving the angle of the long axis over time

Author

Ariana Strandburg-Peshkin (primary author)

NOT YET CODE REVIEWED