diffquo: converts height data into difference quotients

Description

Internal function. Calculates the crude one-sided difference quotients and the second-order difference quotients based on the height data and the observed time points.

Usage

diffquo(data, tobs)

Arguments

data

As in growth.

tobs

As in growth.

Value

YI: An N times (n-1) matrix with rows given by the values of the one-sided difference quotients $y_i, i=1\ldots, n-1$ for the N subjects.
Xtilda: An n by N matrix with columns given by the values of the second-order difference quotients y for the N subjects.