Dear friends and helpers - in the script below, uniroot is called with a
function CHB that calls a function, Charge. On its own, CHB apparently does
what is expected, but from within uniroot, problems appear. An error is
thrown
Error in f(lower, ...) : could not find function "f"
So CHB is not seen or understood from within uniroot?
I'm on windows 10, 64 bit R version 3.5.1 (2018-07-02)
All best wishes
Troels
kw <- 1e-14
TOT <- 1
Pk1 <- 10^-2.16
Pk2 <- 10^-7.21
Pk3 <- 10^-12.32
K <- c(Pk1,Pk2,Pk3)
f <- c(1,1,1)
H <- 10^-7.4
Charge <- function(TOT,f,K,H)
{
num <- c()
num[1] <- K[1]/(f[1]^2*H)
for (i in 2:length(K)) num[i] <- i*prod(K[1:i])/(f[1]^i*f[i]*H^i)
num <- sum(num)
denum <- c()
denum[1] <- 1+ K[1]/(f[1]^2*H)
for (i in 2:length(K)) denum[i] <- prod(K[1:i])/(f[1]^i*f[i]*H^i)
denum <- sum(denum)
num/denum
}
Na <- 0.140
Cl <- 0.1
CHB <- function(Na,Cl,H,K,f,TOT) {Na-Cl+H-kw/(f[1]^2*H)-Charge(TOT,f,K,H)}
H <- uniroot(CHB,interval=c(1e-19,5),tol=.Machine$double.eps,maxiter=100000,
Na=Na,Cl=Cl,K=K,TOT=TOT,f=f)$root
#Error in f(lower, ...) : could not find function "f"
CHB(Na,Cl,10^-7.4,K,f,TOT) # -1.567668 OK right!
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Thanks a lot - f was renamed FF and things are OK BW Troels -----Oprindelig meddelelse----- Fra: Berwin A Turlach <berwin.turlach at gmail.com> Sendt: 19. december 2018 10:27 Til: Troels Ring <tring at gvdnet.dk> Emne: Re: [R] uniroot problem G'day Troels, On Wed, 19 Dec 2018 10:03:09 +0100 "Troels Ring" <tring at gvdnet.dk> wrote:> Dear friends and helpers - in the script below, uniroot is called with > a function CHB that calls a function, Charge. On its own, CHB > apparently does what is expected, but from within uniroot, problems > appear. An error is thrown > > Error in f(lower, ...) : could not find function "f" > > So CHB is not seen or understood from within uniroot?Read the help page of uniroot. The first argument is called "f", it is the function for which the root is searched. In your call:> uniroot(CHB,interval=c(1e-19,5),tol=.Machine$double.eps,maxiter=100000, > Na=Na,Cl=Cl,K=K,TOT=TOT,f=f)$rootYou pass the object "f" (a vector "f <- c(1,1,1)" created earlier in your code) to the argument "f". Presumably there is no function called "f" in your search path, and so R correctly complains that it cannot find the function whose root you are looking for. In R, arguments are passed first by exact matching of actual and formal arguments, then by partial matching and then by position. The easiest fix is probably to rename the object "f" to something else. Cheers, Berwin