[R] Is it possible to recursively update a function?

[Seeker]

Thanks for the input, Uwe. Unfortunately, I need to iteratively update
functions from f1 to f25. Seems I have no choice but set each one
manually.

On Mar 6, 11:45 am, Uwe Ligges <lig... at statistik.tu-dortmund.de>
wrote:
> It is not obvious to me if you can calculate f1, ..., f4, ...
> automatically or have to set them manually. Looks like you need to do it
> manually. In that case I'd suggest to write something along the lines:
>
> dose <- c(-1.47, -1.1, -0.69, -0.42, 0.0, 0.42)
>
> f1 <- function(x) exp(-x)
> f2 <- function(x) f1(x) * (1 - 0.2^x)
> f3 <- function(x) f2(x) * (1 - 0.3^x)
> f4 <- function(x) f3(x) * 0.3^x
>
> calcid <- function(f, dose){
>      denom <- integrate(f, 0, 100)$value
>      alpha <- integrate(function(x) x * f(x), 0, 100)$value / denom
>      which.min(abs(-0.5 * log(0.2^(-1/alpha) - 1) - dose))
>
> }
>
> calcid(f2, dose)
> calcid(f3, dose)
> calcid(f4, dose)
>
> If the hierarchy becomes deeper (i.e. 10 functions or so, it might make
> sense to reduce the number of hierarchical calls for efficiency, but
> that is not necessary for the current setup.
>
> Uwe Ligges
>
> On 05.03.2010 17:34, Ming Zhong wrote:
>
>
>
>
>
> > I was trying to replicate one CRM simulation. The following code works but
> > seems redundant so I want to create a loop.
>
> > ####O'Quigley CRM example 1#####
> > f1<-function(x) exp(-x)
> > dose<-c(-1.47,-1.1,-.69,-.42,0.0,.42)
> > p<-c(0.05,0.1,0.2,0.3,0.5,0.7)
> > y<-c(0,0,1,0,1,1,0,0,0,0,0,0,1,0,0,0,0,0,1,0,0,1,0,1,1)
>
> > f2<-function(x) f1(x)*(1-0.2^x)
> > denom2<-integrate(f2,0,100)$value
> > alpha2<-integrate(function(x) x*f2(x),0,100)$value/denom2
> > id<-which.min(abs(-.5*log(0.2^(-1/alpha2)-1)-dose))  ### id is used to
> > locate the next prob.
>
> > f3<-function(x) f2(x)*(1-.3^x)
> > denom3<-integrate(f3,0,100)$value
> > alpha3<-integrate(function(x) x*f3(x),0,100)$value/denom3
> > id<-which.min(abs(-.5*log(0.2^(-1/alpha3)-1)-dose))
>
> > f4<-function(x) f3(x)*.3^x
> > denom4<-integrate(f4,0,100)$value
> > alpha4<-integrate(function(x) x*f4(x),0,100)$value/denom4
> > id<-which.min(abs(-.5*log(0.2^(-1/alpha4)-1)-dose))
>
> > 2010/3/5 Uwe Ligges<lig... at statistik.tu-dortmund.de>
>
> >> On 05.03.2010 01:40, Carl Witthoft wrote:
>
> >>> My foolish move for this week: I'm going to go way out on a limb and
> >>> guess what the OP wanted was something like this.
>
> >>> i=1, foo = x*exp(-x)
>
> >>> i=2, foo= x^2*exp(-x)
> >>> i=3, foo = x^3*exp(-x)
> >>> .
> >>> .
> >>> .
>
> >>> In which case he really should create a vector bar<-rep(na,5) ,
> >>> and then inside the loop,
>
> >>> bar[i]<-x^i*foo(x)
>
> >> Since in this case foo(x) is independent of i, you are wasting resources.
> >> Moreover you could calculate it for a whole matrix at once. Say you want to
> >> calculate this for i=1, ..., n with n=5 for some (here pseudo random x),
> >> then you could do it simpler after defining some data as in:
>
> >> set.seed(123)
> >> x<- rnorm(10)
> >> n<- 5
>
> >> using the single and probably most efficient line:
>
> >>   outer(x, 1:n, "^") * exp(-x)
>
> >> or if x is a length 1 vector then even simpler:
>
> >> set.seed(123)
> >> x<- rnorm(1)
> >> n<- 5
>
> >>   x^(1:5) * exp(-x)
>
> >> But we still do not know if this is really the question ...
>
> >> Uwe Ligges
>
> >>> Carl
>
> >>> quoted material:
> >>> Date: Thu, 04 Mar 2010 11:37:23 -0800 (PST)
>
> >>> I need to update posterior dist function upon the coming results and
> >>> find the posterior mean each time.
>
> >>> On Mar 4, 1:31 pm, jim holtman<jholt..._at_gmail.com>  wrote:
> >>>   >  What exactly are you trying to do? 'foo' calls 'foo' calls 'foo' ....
> >>>   >  How did you expect it to stop the recursive calls?
>
> >>>   >  On Thu, Mar 4, 2010 at 2:08 PM, Seeker<zhongm..._at_gmail.com>  wrote:
> >>>   >  >  Here is the test code.
>
> >>>   >  >  foo<-function(x) exp(-x)
> >>>   >  >  for (i in 1:5)
> >>>   >  >  {
> >>>   >  >  foo<-function(x) foo(x)*x
> >>>   >  >  foo(2)
> >>>   >  >  }
>
> >>> ______________________________________________
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> >>>https://stat.ethz.ch/mailman/listinfo/r-help
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> >>>http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> >>> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-h... at r-project.org mailing listhttps://stat.ethz.ch/mailman/listinfo/r-help
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>
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