fitpoly2: Polynomial 2 (Quadratic) Model Fit

In tcplfit2: A Concentration-Response Modeling Utility

Polynomial 2 (Quadratic) Model Fit

Description

Function that fits to f(x) = b1*x + b2*x^2 (biphasic), or f(x) = a*(\frac{x}{b} + \frac{x^2}{b^2}) (monotonic only), and returns generic model outputs.

Usage

fitpoly2(
  conc,
  resp,
  bidirectional = TRUE,
  biphasic = TRUE,
  verbose = FALSE,
  nofit = FALSE,
  errfun = "dt4"
)

Arguments

conc	Vector of concentration values NOT in log units.
resp	Vector of corresponding responses.
bidirectional	If TRUE, model can be positive or negative; if FALSE, it will be positive only. (Only in use for monotonic poly2 fitting.)
biphasic	If biphasic = TRUE, allows for biphasic polynomial 2 model fits (i.e. both monotonic and non-monotonic curves). (Note, if FALSE fits f(x) = a*(\frac{x}{b} + \frac{x^2}{b^2}).)
verbose	If TRUE, gives optimization and hessian inversion details.
nofit	If nofit = TRUE, returns formatted output filled with missing values.
errfun	Which error distribution to assume for each point, defaults to "dt4". "dt4" is the original 4 degrees of freedom t-distribution. Another supported distribution is "dnorm", the normal distribution.

Details

(Biphasic Poly2 Model) Zero background is assumed and responses may be biphasic (non-monotonic). Parameters are "b1" (shift along x-axis), "b2" (rate of change, direction, and the shift along y-axis), and error term "er". (Monotonic Poly2 Model) Zero background and monotonically increasing absolute response are assumed. Parameters are "a" (y scale), "b" (x scale), and error term "er". (Biphasic or Monotonic Poly2 Fit) success = 1 for a successful fit, 0 if optimization failed, and NA if nofit = TRUE. cov = 1 for a successful hessian inversion, 0 if it fails, and NA if nofit = TRUE. aic, rme, modl, parameters, and parameter sds are set to NA in case of nofit or failure.

Value

Named list containing: success, aic (Akaike Information Criteria), cov (success of covariance calculation), rme (root mean square error), modl (vector of model values at given concentrations), parameters values, parameter sd (standard deviation) estimates, pars (vector of parameter names), sds (vector of parameter sd names).

Examples

fitpoly2(c(.03,.1,.3,1,3,10,30,100), c(0,.01,.1, .1, .2, .5, 2, 8))

tcplfit2 documentation built on Sept. 24, 2024, 1:07 a.m.