self start for Beta 5-parameter function
Self starter for Beta 5-parameter function
beta5(temp, mu, tb, a, tc, b) SSbeta5(temp, mu, tb, a, tc, b)
temp |
input vector which is normally ‘temperature’ |
mu |
mu parameter (see equation) |
tb |
base (low) temperature at which no expansion accurs |
a |
parameter describing the initial increasing phase |
tc |
critical (high) temperature at which no expasion occurs |
b |
parameter describing the decreasing phase |
For details see the publication by Yin et al. (1995) “A nonlinear model for crop development as a function of temperature ”. Agricultural and Forest Meteorology 77 (1995) 1-16
The form of the equation is:
exp(mu) * (temp - tb)^a * (tc - temp)^b
.
beta5: vector of the same length as x (temp) using the beta5 function
require(minpack.lm) require(ggplot2) ## Temperature response example data(maizeleafext) ## Fit model fit <- nlsLM(rate ~ SSbeta5(temp, mu, tb, a, tc, b), data = maizeleafext) ## Visualize ndat <- data.frame(temp = 0:45) ndat$rate <- predict(fit, newdata = ndat) ggplot() + geom_point(data = maizeleafext, aes(temp, rate)) + geom_line(data = ndat, aes(x = temp, y = rate))
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