Nothing
#Example 2: Wood function
#
wood.f <- function(x){
res <- 100*(x[1]^2-x[2])^2+(1-x[1])^2+90*(x[3]^2-x[4])^2+(1-x[3])^2+
10.1*((1-x[2])^2+(1-x[4])^2)+19.8*(1-x[2])*(1-x[4])
return(res)
}
#gradient:
wood.g <- function(x){
g1 <- 400*x[1]^3-400*x[1]*x[2]+2*x[1]-2
g2 <- -200*x[1]^2+220.2*x[2]+19.8*x[4]-40
g3 <- 360*x[3]^3-360*x[3]*x[4]+2*x[3]-2
g4 <- -180*x[3]^2+200.2*x[4]+19.8*x[2]-40
return(c(g1,g2,g3,g4))
}
#hessian:
wood.h <- function(x){
h11 <- 1200*x[1]^2-400*x[2]+2; h12 <- -400*x[1]; h13 <- h14 <- 0
h22 <- 220.2; h23 <- 0; h24 <- 19.8
h33 <- 1080*x[3]^2-360*x[4]+2; h34 <- -360*x[3]
h44 <- 200.2
H <- matrix(c(h11,h12,h13,h14,h12,h22,h23,h24,
h13,h23,h33,h34,h14,h24,h34,h44),ncol=4)
return(H)
}
wood.fgh <- function(x){
fval <- wood.f(x)
gval <- wood.g(x)
hval <- wood.h(x)
attr(fval,"gradient") <- gval
attr(fval,"hessian")<- hval
fval
}
#################################################
x0 <- c(-3,-1,-3,-1) # Wood standard start
library(snewton)
cat("This FAILS to find minimum\n")
wd <- snewton(x0, fn=wood.f, gr=wood.g, hess=wood.h, control=list(trace=2))
print(wd)
wdm <- snewtonm(x0, fn=wood.f, gr=wood.g, hess=wood.h, control=list(trace=2))
print(wdm)
cat("\n\n nlm() gives similar results\n")
tnlm <- nlm(wood.fgh, x0, print.level=2)
print(tnlm)
Any scripts or data that you put into this service are public.
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.