R help - Aug 2011 - sapply( ) a loop function

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]]

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]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 
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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
>
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>