logistic {AgroR} R Documentation

## Analysis: Logistic regression

### Description

Logistic regression is a very popular analysis in agrarian sciences, such as in fruit growth curves, seed germination, etc...The logistic function performs the analysis using 3 or 4 parameters of the logistic model, being imported from the LL function .3 or LL.4 of the drc package (Ritz & Ritz, 2016).

### Usage

logistic(
trat,
resp,
npar = "LL.3",
error = "SE",
ylab = "Dependent",
xlab = expression("Independent"),
theme = theme_classic(),
legend.position = "top",
r2 = "all",
width.bar = NA,
scale = "none",
textsize = 12,
font.family = "sans"
)


### 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_bw()) legend.position Legend position (default is c(0.3,0.8)) r2 Coefficient of determination of the mean or all values (default is all) width.bar Bar width scale Sets x scale (default is none, can be "log") textsize Font size font.family Font family (default is sans)

### Details

The three-parameter log-logistic function with lower limit 0 is

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

The four-parameter log-logistic function is given by the expression

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

The function is symmetric about the inflection point (e).

### Value

The function allows the automatic graph and equation construction of the logistic model, provides important statistics, such as the Akaike (AIC) and Bayesian (BIC) inference criteria, coefficient of determination (r2), square root of the mean error ( RMSE).

### 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

data("emerg")
attach(emerg)

logistic(time, resp)


[Package AgroR version 1.2.2 Index]