warrendreyer_2006: Warren-Dreyer model for fitting thermal performance curves

In padpadpadpad/rTPC: Fitting and Analysing Thermal Performance Curves

Warren-Dreyer model for fitting thermal performance curves

Description

Warren-Dreyer model for fitting thermal performance curves

Usage

warrendreyer_2006(temp, rmax, topt, a)

Arguments

temp	temperature in degrees centigrade
rmax	maximum performance/value of the trait
topt	temperature of max performance (ºC)
a	shape parameter

Details

Equation:

rate = R_{\text{max}} \cdot \exp{\left[-0.5 \cdot \left(\frac{\ln{\frac{T}{T_{\text{opt}}}}}{a}\right)^2\right]}

Start values in get_start_vals are derived from the data or sensible values from the literature.

Limits in get_lower_lims and get_upper_lims are derived from the data or based extreme values that are unlikely to occur in ecological settings.

Value

a numeric vector of rate values based on the temperatures and parameter values provided to the function

Note

Generally we found this model easy to fit.

Author(s)

Francis Windram

References

Warren, C. R. & Dreyer, E. Temperature response of photosynthesis and internal conductance to CO2: results from two independent approaches. J. Exp. Bot. 57, 3057–3067 (2006).

Examples

# load in ggplot
library(ggplot2)

# subset for the first TPC curve
data('chlorella_tpc')
d <- subset(chlorella_tpc, curve_id == 1)

# get start values and fit model
start_vals <- get_start_vals(d$temp, d$rate, model_name = 'warrendreyer_2006')
# fit model
mod <- nls.multstart::nls_multstart(rate~warrendreyer_2006(temp = temp, rmax, topt, a),
data = d,
iter = c(3,3,3),
start_lower = start_vals - 10,
start_upper = start_vals + 10,
lower = get_lower_lims(d$temp, d$rate, model_name = 'warrendreyer_2006'),
upper = get_upper_lims(d$temp, d$rate, model_name = 'warrendreyer_2006'),
supp_errors = 'Y',
convergence_count = FALSE)

# look at model fit
summary(mod)

# get predictions
preds <- data.frame(temp = seq(min(d$temp), max(d$temp), length.out = 100))
preds <- broom::augment(mod, newdata = preds)

# plot
ggplot(preds) +
geom_point(aes(temp, rate), d) +
geom_line(aes(temp, .fitted), col = 'blue') +
theme_bw()

padpadpadpad/rTPC documentation built on Feb. 21, 2025, 5:30 a.m.