CD_model: Analysis: Logistic regression Cedergreen-Ritz-Streibig model

In AgronomiaR/seedreg: Regression Analysis for Seed Germination as a Function of Temperature

Description

The 'CRS.4' and 'CRS.5' logistical models provide Brain-Cousens modified logistical models to describe u-shaped hormesis. This model was extracted from the 'drc' package and adapted for temperature analysis in seed germination

Usage

CD_model(
  trat,
  resp,
  npar = "CRS.4",
  error = "SE",
  ylab = "Germination (%)",
  xlab = expression("Temperature ("^"o" * "C)"),
  theme = theme_classic(),
  legend.position = "top",
  cardinal = 0,
  r2 = "all",
  scale = "none"
)

Arguments

trat	Numerical or complex vector with treatments
resp	Numerical vector containing the response of the experiment.
npar	Number of model parameters
error	Error bar (It can be SE - default, SD or FALSE)
ylab	Variable response name (Accepts the expression() function)
xlab	treatments name (Accepts the expression() function)
theme	ggplot2 theme (default is theme_classic())
legend.position	legend position (default is c(0.3,0.8))
cardinal	defines the value of y considered extreme (default considers 0 germination)
r2	coefficient of determination of the mean or all values (default is all)
scale	Sets x scale (default is none, can be "log")

Details

The four-parameter model is given by the expression:

f(x) = 0 + \frac{d-0+f \exp(-1/x)}{1+\exp(b(\log(x)-\log(e)))}

while the five-parameter is:

f(x) = c + \frac{d-c+f \exp(-1/x)}{1+\exp(b(\log(x)-\log(e)))}

Value

The function returns the coefficients and respective p-values; statistical parameters such as AIC, BIC, pseudo-R2; cardinal and optimal temperatures and the graph using ggplot2 with the equation.

Note

if the maximum predicted value is equal to the maximum x, the curve does not have a maximum point within the studied range. If the minimum value is less than the lowest point studied, disregard the value.

Author(s)

Model imported from the drc package (Ritz et al., 2016)

Gabriel Danilo Shimizu

Leandro Simoes Azeredo Goncalves

References

Seber, G. A. F. and Wild, C. J (1989) Nonlinear Regression, New York: Wiley \& Sons (p. 330).

Ritz, C.; Strebig, J.C.; Ritz, M.C. Package 'drc'. Creative Commons: Mountain View, CA, USA, 2016.

Examples

library(seedreg)
data("aristolochia")
attach(aristolochia)
CD_model(trat,resp)

AgronomiaR/seedreg documentation built on May 19, 2021, 12:12 p.m.