R Under development (unstable) (2025-08-19 r88650 ucrt) -- "Unsuffered Consequences"
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> 
> require(nlraa)
Loading required package: nlraa
> require(ggplot2)
Loading required package: ggplot2
> ##library(agridat)
> 
> if(FALSE){
+   
+   data("hernandez.nitrogen")
+ 
+   hn <- hernandez.nitrogen
+   
+   ggplot(data = hn, aes(x = nitro, y = yield)) + 
+     facet_wrap(~loc) + 
+     geom_point()
+   
+   fm1 <- lm(yield ~ nitro + I(nitro^2), data = hn)
+   fm2 <- nls(yield ~ SSlinp(nitro, a, b, xs), data = hn)
+   fm3 <- nls(yield ~ SSquadp3xs(nitro, a, b, xs), data = hn)
+   fm4 <- nls(yield ~ SSquadp(nitro, a, b, c, xs), data = hn)
+   fm5 <- nls(yield ~ SSquadpq(nitro, a, b, xs, ldxs = 4.2),
+              start = list(a = 7, b = 0.05, xs = 200),
+              data = hn)
+   
+   ## This does not work
+   ## fm6 <- minpack.lm::nlsLM(yield ~ SSquadpq(nitro, a, b, xs, ldxs), data = hn)
+   
+   ## Interestingly they all fit better than the quadratic
+   IC_tab(fm1, fm2, fm3, fm4, fm5)
+   
+   ggplot(data = hn, aes(x = nitro, y = yield)) + 
+     geom_point() + 
+     geom_line(aes(y = fitted(fm1), color = "Q")) + 
+     geom_line(aes(y = fitted(fm2), color = "LP")) + 
+     geom_line(aes(y = fitted(fm3), color = "QP3-xs")) + 
+     geom_line(aes(y = fitted(fm4), color = "QP")) + 
+     geom_line(aes(y = fitted(fm5), color = "QPQ"))
+   
+ }
> 
> 
> proc.time()
   user  system elapsed 
   2.51    0.29    2.76