estDerivs: Estimates first and second derivatives of an oberved state...

In ebmtnprof/qid: Version of "rties" to accompany "Quantifying Interpersonal Dynamics"

Description

This function makes use of 2 functions written by Steven Boker, "gllaWMatrix" and "gllaEmbed" which are available on his website, http://people.virginia.edu/~smb3u/. It fits an individual linear oscillator model for each person at different combinations of the input parameters (tau, embeds) and returns the input values and period of oscillation that maximize the R^2 for each person. It also estimates first and second derivatives of the observed state variable for each person at the input values that maximize the R^2 for that person and returns a dataframe that contains them.

Usage

estDerivs(basedata, taus, embeds, delta, coVar = FALSE)

Arguments

basedata	A dataframe that was produced with the "dataPrep" function.
taus	A vector containing the values of tau to use. Tau indicates the number of time points to lag in the lagged data matrix (see Boker, S.M., Deboeck, P.R., Edler, C., & Keel, P.K. (2010). Generalized local linear approximation of derivatives from time series. In S.M. Chow & E. Ferrer (Eds.), Statistical Methods for Modeling Human Dynamics: An Interdisciplinary Dialogue (pp. 161-178). New York, NY: Taylor & Francis Group). The first derivative is estimated as the mean of the two adjacent slopes across that number of lags, e.g., if tau = 2 then the estimate of the first derivative at time = t is based on the mean of the slopes left and right of time t across 2 observations each. The second derivative is the difference in the two slopes with respect to time. Tau = 1 is sensitive to noise and increasing its value acts as smoothing.
embeds	A vector containing the values of embeds to use. Embeds indicates the number of columns in the lagged data matrix. The minimum = 3 for 2nd order derivatives and higher values increase smoothing.
delta	A value indicating the inter-observation interval. For example, if delta = 2, then every second observation is used in the estimation process.

Value

The function returns a list including: 1) "data" which is a dataframe containing first and second derivative estimates of an observed state variable, and 2) "fitTable" which shows the maximal R^2 achieved for each person for an individual oscillator model, along with the associated tau, embed and estimated period of oscillation.

ebmtnprof/qid documentation built on May 13, 2019, 6:08 p.m.