SSasympOrig

0th

Percentile

Self-Starting Nls Asymptotic Regression Model through the Origin

This selfStart model evaluates the asymptotic regression function through the origin and its gradient. It has an initial attribute that will evaluate initial estimates of the parameters Asym and lrc for a given set of data.

Keywords
models
Usage
SSasympOrig(input, Asym, lrc)
Arguments
input

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

Asym

a numeric parameter representing the horizontal asymptote.

lrc

a numeric parameter representing the natural logarithm of the rate constant.

Value

a numeric vector of the same length as input. It is the value of the expression Asym*(1 - exp(-exp(lrc)*input)). If all of the arguments Asym and lrc are names of objects, the gradient matrix with respect to these names is attached as an attribute named gradient.

See Also

nls, selfStart

Aliases
  • SSasympOrig
Examples
library(stats) # NOT RUN { Lob.329 <- Loblolly[ Loblolly$Seed == "329", ] SSasympOrig(Lob.329$age, 100, -3.2) # response only local({ Asym <- 100; lrc <- -3.2 SSasympOrig(Lob.329$age, Asym, lrc) # response and gradient }) getInitial(height ~ SSasympOrig(age, Asym, lrc), data = Lob.329) ## Initial values are in fact the converged values fm1 <- nls(height ~ SSasympOrig(age, Asym, lrc), data = Lob.329) summary(fm1) # } # NOT RUN { ## Visualize the SSasympOrig() model parametrization : xx <- seq(0, 5, len = 101) yy <- 5 * (1- exp(-xx * log(2))) stopifnot( all.equal(yy, SSasympOrig(xx, Asym = 5, lrc = log(log(2)))) ) require(graphics) op <- par(mar = c(0, 0, 3.5, 0)) plot(xx, yy, type = "l", axes = FALSE, ylim = c(0,5), xlim = c(-1/4, 5), xlab = "", ylab = "", lwd = 2, main = quote("Parameters in the SSasympOrig model"~~ f[phi](x))) mtext(quote(list(phi[1] == "Asym", phi[2] == "lrc"))) usr <- par("usr") arrows(usr[1], 0, usr[2], 0, length = 0.1, angle = 25) arrows(0, usr[3], 0, usr[4], length = 0.1, angle = 25) text(usr[2] - 0.2, 0.1, "x", adj = c(1, 0)) text( -0.1, usr[4], "y", adj = c(1, 1)) abline(h = 5, lty = 3) axis(2, at = 5*c(1/2,1), labels= expression(frac(phi[1],2), phi[1]), pos=0, las=1) arrows(c(.3,.7), 5/2, c(0, 1 ), 5/2, length = 0.08, angle = 25) text( 0.5, 5/2, quote(t[0.5])) text( 1 +.4, 5/2, quote({f(t[0.5]) == frac(phi[1],2)}~{} %=>% {}~~{t[0.5] == frac(log(2), e^{phi[2]})}), adj = c(0, 0.5)) par(op) # }
Documentation reproduced from package stats, version 3.5.0, License: Part of R 3.5.0

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