# [R] Help with iteration using while loop

From: Subodh Acharya <shoebodh_at_gmail.com>
Date: Fri, 04 Jun 2010 13:30:18 -0400

Hello everyone,

I am trying to use while loop to iterate a function until convergence. But I am having problem when I try to use a fixed number of iterations. Say I want to use maximum iteration of 150. If the value don't converge within maximum iteration, show warning of no convergence.

Currently I don't have non- convergence problem so I think my code works fine. But in future I may encounter such problem that are likely to not converge easily.

Below is my function that is working when I don't provide maximum iteration.

iter<- function (Fpi, Time, tolerance){

```S = 22.4
Ts = 0.499
Ti = 0.25
```

K = 0.044
r<- 1.5
M = Ts- Ti
Ks = 0.044
```     Fpt = K*Time + M*S*log(1+ Fpi/(M*S))
while((Fpt-Fpi) > tolerance) {
Fpi = Fpt
Fpt = K*Time + M*S*log(1+ Fpi/(M*S))
Fp0 = Fpt
```

}
return(Fpt)
}

x<- iter(Fpi = 0.224, Time = 0.2, tolerance = 0.000001)

But I want do something like this ( conceptually) for( i in 2:itermax) {
Fpt[i] = K*Time + M*S*log(1+ Fpi/(M*S)) if((Fpt[i]- Fpt[i-1])<= tolerance) break print(Fpt[i]
}

something like this.

any kind of help is highly appreciated.
thank you

```--
Acharya, Subodh

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