R help - Dec 2007 - 4 questions regarding hypothesis testing, survey package, ts on samples, plotting

Good morning!

I have 4 questions which trouble me:

1. I want to test the hypothesis that the 2 proportions (the mean of a binomial)
which come from 2 different samples are equal. I want to use the following
function
z= (p1-p2)/ sqrt((p1(1-p1)/n1)+(p2(1-p2)/n2)) which is one of the standard
formulas  for  this case. Is there such a function in R?

p1=the proportion from the first sample
n1=the first sample size
p1=the proportion from the second sample
n2=the second sample size

2. How can i find the median of a variable in survey package?
a<-c(1:10)
b<-sample(1:20, 10, replace=T)
b1<-sample(0:1, 10, replace=T)
c<-data.frame(a,b, b1)
library(survey)
design<-svydesign(id=~1, data=c)
svymean(~b, design)

svymean gives me the mean, but what function gives me the svymedian, and what
function gives me the svyproportion  for b1?
I want to know the median for a metric variable and the proportion for a
binomial variable ?

3. Could time series analysis (arima/arma)  be applied on data that are obtained
from a sample?. Eg: Say I have data from the same sample in 40 moments. Could I
use arima/arma on the series? Or must i have data for the whole population like
data from the Statistical Office on investment, inflation, demographics and so
on?

4. I want to modify the scale of my axes within a plot but i really could not
find  this option. I think  there is such an option, but i can not find it.
 x<-rnorm(100, 100, 3)
 x<-ts(x, frequency=12)
 acf(x)
 plot(x)
On the above example, i want to a scale like this 95,96,97,98,....104,105  (on
y) and 1,2,3,4,...7,8 (on x).

Thank you very much and have a great day!
      

       
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On 19/12/07 8:39 PM, eugen pircalabelu wrote:
> 2. How can i find the median of a variable in survey package?
> a<-c(1:10)
> b<-sample(1:20, 10, replace=T)
> b1<-sample(0:1, 10, replace=T)
> c<-data.frame(a,b, b1)
> library(survey)
> design<-svydesign(id=~1, data=c)
> svymean(~b, design)
> 
> svymean gives me the mean, but what function gives me the svymedian, and
what function gives me the svyproportion  for b1?
> I want to know the median for a metric variable and the proportion for a
binomial variable ?
The svyquantile function will give you the median, e.g.
svyquantile(~b, design, 0.5, interval.type="score")

Since a proportion is just the mean of a 0/1 variable, you can use 
svymean for that, e.g.
svymean(~b1, design)

HTH,
James
-- 
James Reilly
Department of Statistics, University of Auckland
Private Bag 92019, Auckland, New Zealand

eugen pircalabelu <eugen_pircalabelu at yahoo.com> wrote in
news:187205.27181.qm at web38605.mail.mud.yahoo.com: > 
> I have 4 questions which trouble me:
> 
snip 1-3
> 
> 4. I want to modify the scale of my axes within a plot but i really
> could not find  this option. I think  there is such an option, but i
> can not find it.  
>  x<-rnorm(100, 100, 3)
>  x<-ts(x, frequency=12)
>  acf(x)
>  plot(x)
> On the above example, i want to a scale like this
> 95,96,97,98,....104,105  (on y) and 1,2,3,4,...7,8 (on x). 
Instead of looking at ?plot, try:
?plot.default # see the xlim and ylim arguments.

-- 
David Winsemius