ggtrendline (version 1.0.3)

SSpower2P: Self-Starting Nls 'power2P' Regression Model

Description

This selfStart model evaluates the power regression function (formula as: y=a*x^b). It has an initial attribute that will evaluate initial estimates of the parameters 'a' and 'b' for a given set of data.

Usage

SSpower2P(predictor, a, b)

Arguments

predictor

a numeric vector of values at which to evaluate the model.

a, b

The numeric parameters responding to the exp2P model.

Value

No return value (called for side effects).

See Also

ggtrendline, SSexp3P, SSpower3P, nls, selfStart

Examples

# NOT RUN {
library(ggtrendline)
x<-1:5
y<-c(2,4,8,20,25)
xy<-data.frame(x,y)
getInitial(y ~ SSpower2P(x,a,b), data = xy)
## Initial values are in fact the converged values

fitpower2P <- nls(y~SSpower2P(x,a,b), data=xy)
summary(fitpower2P)

prediction <- predFit(fitpower2P , data.frame(x=x), se.fit = TRUE,
                          level = 0.95, interval = "confidence")
yfitpower2P <- prediction$fit
yfitpower2P # output a matrix of predictions and bounds with column names fit, lwr, and upr.

# }