# [R] uniroot problem

Troels Ring tring @ending from gvdnet@dk
Wed Dec 19 10:03:09 CET 2018

```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!

[[alternative HTML version deleted]]

```

More information about the R-help mailing list