self start for plateau-exponential function
Self starter for an plateau-exponential function
pexpf(x, a, xs, c) SSpexpf(x, a, xs, c)
x |
input vector (x) |
a |
represents the value for the plateau |
xs |
represents the breakpoint at which the plateau ends |
c |
represents the exponential rate |
The equation is: for x < xs: y = a and x >= xs: a * exp(c * (x-xs)).
a numeric vector of the same length as x containing parameter estimates for equation specified
pexpf: vector of the same length as x using the pexpf function
require(ggplot2) set.seed(1234) x <- 1:30 y <- pexpf(x, 20, 15, -0.2) + rnorm(30, 0, 1) dat <- data.frame(x = x, y = y) fit <- nls(y ~ SSpexpf(x, a, xs, c), data = dat) ## plot ggplot(data = dat, aes(x = x, y = y)) + geom_point() + geom_line(aes(y = fitted(fit)))
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