[R] sapply( ) a loop function

[Daniel Malter]

I am not sure what purpose the while loop has. However, the main problem
seems to be that you need to put:

i<-sample(1:(n-40),1) #This sample from 1 to n-40

rather than 

i<-sample(1:n-40,1) #this samples one 1:n and then subtracts 40

Otherwise, you may get negative index values

Best,
Daniel



bignami83 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
> 
> 
> 	[[alternative HTML version deleted]]
> 
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