[R] Using function 'boot on a bi-polar sample'
Prof Brian Ripley
ripley at stats.ox.ac.uk
Tue May 10 08:00:07 CEST 2005
On Tue, 10 May 2005, Briggs, Meredith M wrote:
> I'm not sure I'm using boot correctly:
You are not using argument `i'. Have you read the reference: `boot' is
support software for a book? (Or even the definition of `statistic' on
the help page?) The bootstrap sample in your case is x[i], not x.
> I have a list of values for a variable in BUCKET[, j] I want to use
> function 'boot' to estimate a confidence interval on the mean of the
> non-zero data. The data can be bi-polar or skewed. Is this the correct
> use of boot to establish a mean and standard deviation or median and
> percentiles?
>
>
> x<-BUCKET[, j]
> mean.fun<-function(x,i) {mean(x[x>0])}
> median.fun<-function(x,i) {median(x[x>0])}
> print(mean.fun(x))
> print(median.fun(x))
> B.mean<-boot(x,mean.fun,R=999)
> B.median<-boot(x,mean.fun,R=999)
> print(B.mean)
> print(B.median)
>
> I need the 'boot' function to sample repeatedly from the density
> distribution of the raw data and calculate means, medians etc.
>
> How do I pull out the mean, median, deviations and percentiles into
> variables within R?
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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