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> # http://r.789695.n4.nabble.com/newton-method-td2306111.html#a2306111
> # R-help, 29-07-2010: newton.method
> 
> library(nleqslv)
> 
> f <- function(x) 2.5*exp(-0.5*(2*0.045 - x)) + 2.5*exp(-0.045) + 2.5*exp(-1.5*x) - 100
> 
> g1 <- function(x) 0.5*2.5*exp(-0.5*(2*0.045 - x)) - 1.5*2.5*exp(-1.5*x)
> g2 <- function(x) matrix(0.5*2.5*exp(-0.5*(2*0.045 - x)) - 1.5*2.5*exp(-1.5*x), nrow=1,ncol=1)
> 
> xu.1 <- uniroot(f,c(-3,0), tol=1e-8)$root
> xu.2 <- uniroot(f,c( 6,8), tol=1e-8)$root
> 
> xg1.1 <- nleqslv(-2,f,g1)$x
> xg2.1 <- nleqslv(-2,f,g2)$x
> 
> xg1.2 <- nleqslv(8,f,g1)$x
> xg2.2 <- nleqslv(8,f,g2)$x
> 
> all.equal(xg1.1, xu.1)
[1] TRUE
> all.equal(xg1.2, xu.2)
[1] TRUE
> all.equal(xg1.2, xg2.2)
[1] TRUE
> 
> all.equal(xg2.1, xu.1)
[1] TRUE
> all.equal(xg2.2, xu.2)
[1] TRUE
> all.equal(xg1.2, xg2.2)
[1] TRUE
> 
> proc.time()
   user  system elapsed 
   0.15    0.04    0.18