prepare: Prepares a multivariate data set for use in nls / evrunge

In nlsrk: Runge-Kutta Solver for Function nls()

Description

Utility :
Modifies a multivariate data.frame for fitting a nonlinear model defined by a system of first order Ordinary Differential Equations. In the original data.frame, the data must be arrange in nfunct + 1 columns, nfunct being the dimension of the ODE system. One of the column must be the observation times (or in general the observations of the independent variable). The others colums are the observations of the functions. prepare returns the same data set with a single column for time (repeated nfunct times), and a single column for the concatenated observations. A third column is created as a factor indexing the original column (1 for the first, 2 for the second, etc)

Usage

prepare(x = data.frame, ntime = 1, cols = c(2:(length(x[1, ]))))

Arguments

x	a data.frame : one column for time and one for each function
ntime	numeric : the number of the column coding for time (independent variable)
cols	numeric vector : the numbers of the columns corresponding to each dependent variable

Details

Prepares the data set as an entry for nls which is basically univariate. The formula in nls must involve evrunge. As nls considers the observations as univariate, the criterion used in the least-square process is that of the trace of the variance-covariance matrix of the residuals.

Value

A data.frame with columns :

t	time repeated as many times as necessary
y	concatenated observed trajectories
traj	factor : number of the trajectory

Author(s)

Jean-Sebastien Pierre [e-mail]

See Also

frunge, dfdt,multirunge,evrunge,sys,nls

Examples

data(syslin.don)
syslin<-prepare(syslin.don)
summary(syslin)

nlsrk documentation built on May 1, 2019, 8:48 p.m.