[R] recursively divide a value to get a sequence

[René Capell]

Hi Anne-Marie,

maybe its not particularly elegant, but this function does the trick:

> dilute<-function(val,div,len){
+   res<-rep(val,len)
+   res<-res/div^c(0:(len-1))
+   res[len]<-0
+   res
+   }
> dilute(15000,5,9)

Cheers, René



> -----Ursprüngliche Nachricht-----
> Von: "Anne-Marie Ternes" <amternes at gmail.com>
> Gesendet: 09.07.08 14:12:16
> An: r-help at r-project.org
> Betreff: [R] recursively divide a value to get a sequence


> Hi,
> 
> if given the value of, say, 15000, I would like to be able to divide
> that value recursively by, say, 5, and to get a vector of a determined
> length, say 9, the last value being (set to) zero- i.e. like this:
> 
> 15000 3000 600 120 24 4.8 0.96 0.192 0
> 
> These are in fact concentration values from an experiment. For my
> script, I get only the starting value (here 15000), and the factor by
> which concentration is divided for each well, the last one having, by
> definition, no antagonist at all.
> 
> I have tried to use "seq", but it can "only" do positive or negative
> increment. I didn't either find a way with "rep", "sweep" etc. These
> function normally start from an existing vector, which is not the case
> here, I have only got a single value to start with.
> 
> I suppose I could do something "loopy", but I'm sure there is a better
> way to do it.
> 
> Thanks a lot for your help, hope the question is not too dumb...
> 
> Anne-Marie
> 
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