[R] sapply( ) a loop function

[Dennis Murphy]

Hi:

samp_func() doesn't return anything. Either (1) type test as the last
line of the function body or (2) don't assign the last sum to an
object.

HTH,
Dennis

On Thu, Aug 11, 2011 at 1:59 PM, Sean Bignami <bignami83 at gmail.com> wrote:
> Hello R-universe...
>
> I am having trouble writing a function which contains a loop so I can sapply() it to a list of data frames
>
> Each data frame has 241 observations of 15 variables. My loop takes a random sample of one row until the 40 consecutive rows after the sample have a d2p(variable) sum greater than 5.
>
> here is my loop code (it works fine when applied to a 241 observation data frame):
>
>        n<-241
>        test<-0
>        while(test<5){
>                i<-sample(1:n-40,1)
>                x<-my.data.frame[seq(from=i, to=i+40),]
>                test<-sumx[,"d2p"],na.rm=TRUE)
>                }; i ; test
>
> I need this loop to be applied to EACH DATA FRAME in a list of 360 data frames created by splitting my master data frame, d, by each fish number. (contains observations for 360 fish, each with 241 observations of 15 variables).
>
>        split.df<-split(d,d$fish)
>
> I'm kind of new at writing functions, so I'm sure this probably doesn't make much sense, but here is what I tried for the function:
>
>        samp.func<-function(f) {
>        n<-241
>        test<-0
>        while(test<5){
>                i<-sample(1:n-40,1)
>                x<-f[seq(from=i, to=i+40),]
>                test<-sum(x[,"d2p"],na.rm=TRUE)
>                }}
>
> and then tried to apply it to my list of data frames (NOT WORKING):
>
>        sapply(split.df,samp.func)
>
> I'm pretty sure I'm missing some way to instruct that I want the loop to cycle through for each item (data frame) in my split.df list. I've tried to play around with including "for" loops with no avail...
>
> any ideas?
>
>
>
> here is code for a simplified mock single-fish data frame (i.e. one item in my split.df list) to plug into the loop if you want to try it.
>
> fish<-rep(1,241)
> d2p<-seq((50/241),50,(50/241))
> my.data.frame<-data.frame(fish,d2p)
>
> thanks!!
> Sean
>
>
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>
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