piecewise_model: Analysis: Piecewise regression

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

Description

Fit a degree 1 spline with 1 knot point where the location of the knot point is unknown.

Usage

piecewise_model(
  trat,
  resp,
  middle = 1,
  CI = FALSE,
  bootstrap.samples = 1000,
  sig.level = 0.05,
  error = "SE",
  ylab = "Germination (%)",
  xlab = expression("Temperature ("^"o" * "C)"),
  theme = theme_classic(),
  cardinal = 0,
  legend.position = "top"
)

Arguments

trat	Numerical or complex vector with treatments
resp	Numerical vector containing the response of the experiment.
middle	A scalar in [0,1]. This represents the range that the change-point can occur in. 0 means the change-point must occur at the middle of the range of x-values. 1 means that the change-point can occur anywhere along the range of the x-values.
CI	Whether or not a bootstrap confidence interval should be calculated. Defaults to FALSE because the interval takes a non-trivial amount of time to calculate
bootstrap.samples	The number of bootstrap samples to take when calculating the CI.
sig.level	What significance level to use for the confidence intervals.
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())
cardinal	defines the value of y considered extreme (default considers 0 germination)
legend.position	legend position (default is c(0.3,0.8))

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 SiZer package

Gabriel Danilo Shimizu

Leandro Simoes Azeredo Goncalves

References

Chiu, G. S., R. Lockhart, and R. Routledge. 2006. Bent-cable regression theory and applications. Journal of the American Statistical Association 101:542-553.

Toms, J. D., and M. L. Lesperance. 2003. Piecewise regression: a tool for identifying ecological thresholds. Ecology 84:2034-2041.

Examples

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

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