R help - Nov 2009 - resampling problem counting number of means above a specific value

I am trying to modify some code from Good 2005.

I am trying  to resample the mean of 8 values and then count how many
times the resampled mean is greater than 10. But my count of means
above 10 is coming out as zero, which I know isn't correct.

I would appreciate it if someone could look at the code below and tell
me what I am doing wrong.

Many thanks,

Graham
> LL<- c(12.5,17,12,11.5,9.5,15.5,16,14)
> N<-1000
> n<-length(LL)
> threshold<-10
> cnt<-0
> for(i in 1:N){
+ LLb <- sample (LL, n, replace=TRUE)
+ if (mean(LLb)<=threshold) cnt<-cnt+1
+ }
> cnt
[1] 0

On Nov 15, 2009, at 12:12 PM, Graham Smith wrote:
> I am trying to modify some code from Good 2005.
>
> I am trying  to resample the mean of 8 values and then count how many
> times the resampled mean is greater than 10. But my count of means
> above 10 is coming out as zero, which I know isn't correct.
If that is your goal, then why are you using "<=" and not
">" in your
test?

 > for(i in 1:N){
+  LLb <- sample (LL, n, replace=TRUE)
+  if (mean(LLb) > threshold) cnt<-cnt+1
+  }
 > cnt
[1] 1000
>
> I would appreciate it if someone could look at the code below and tell
> me what I am doing wrong.
>
> Many thanks,
>
> Graham
>
>> LL<- c(12.5,17,12,11.5,9.5,15.5,16,14)
>> N<-1000
>> n<-length(LL)
>> threshold<-10
>> cnt<-0
>> for(i in 1:N){
> + LLb <- sample (LL, n, replace=TRUE)
> + if (mean(LLb)<=threshold) cnt<-cnt+1
> + }
>> cnt
> [1] 0
>
> ______________________________________________
> 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.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT

try the following:

LL <- c(12.5,17,12,11.5,9.5,15.5,16,14)
n <- length(LL)
N <- 1000
threshold <- 10

smpls <- sample(LL, N*n, replace = TRUE)
dim(smpls) <- c(n, N)
cnt <- sum(colMeans(smpls) > threshold)
cnt


I hope it helps.

Best,
Dimitris


Graham Smith wrote:
> I am trying to modify some code from Good 2005.
> 
> I am trying  to resample the mean of 8 values and then count how many
> times the resampled mean is greater than 10. But my count of means
> above 10 is coming out as zero, which I know isn't correct.
> 
> I would appreciate it if someone could look at the code below and tell
> me what I am doing wrong.
> 
> Many thanks,
> 
> Graham
> 
>> LL<- c(12.5,17,12,11.5,9.5,15.5,16,14)
>> N<-1000
>> n<-length(LL)
>> threshold<-10
>> cnt<-0
>> for(i in 1:N){
> + LLb <- sample (LL, n, replace=TRUE)
> + if (mean(LLb)<=threshold) cnt<-cnt+1
> + }
>> cnt
> [1] 0
> 
> ______________________________________________
> 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.
> 
-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

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