## data
set.seed(1)
n <- 25
xy <- data.frame(
x = (1:n) / n,
y = 2.5 * exp(-1.5 * (1:n) / n) + 1 + rnorm(n, sd = 0.1)
)
## model
obj1 <- gsl_nls(fn = y ~ A * exp(-lam * x), data = xy, start = c(A = 1, lam = 1))
obj2 <- gsl_nls(fn = y ~ A * exp(-lam * x) + b, data = xy,
start = c(A = 1, lam = 1, b = 0))
anova(obj1, obj2)
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