self start for an exponential function
Self starter for a simple exponential function
expf(x, a, c) SSexpf(x, a, c)
x |
input vector (x) |
a |
represents the value at x = 0 |
c |
represents the exponential rate |
This is the exponential function
y = a * exp(c * x)
For more details see: Archontoulis and Miguez (2015) - (doi:10.2134/agronj2012.0506).
a numeric vector of the same length as x containing parameter estimates for equation specified
expf: vector of the same length as x using the profd function
require(ggplot2) set.seed(1234) x <- 1:15 y <- expf(x, 10, -0.3) + rnorm(15, 0, 0.2) dat <- data.frame(x = x, y = y) fit <- nls(y ~ SSexpf(x, a, c), data = dat) ## plot ggplot(data = dat, aes(x = x, y = y)) + geom_point() + geom_line(aes(y = fitted(fit)))
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