[R-br] correlação de pearson

[alanarocha em sapo.pt]

eu tentei instalar os packages para a correlação e acontece-me o seguinte:
> install.packages("ppcor")
--- Please select a CRAN mirror for use in this session ---
Warning: unable to access index for repository  
http://cran.fiocruz.br/bin/windows/contrib/2.15
Warning: unable to access index for repository  
http://www.stats.ox.ac.uk/pub/RWin/bin/windows/contrib/2.15
Warning messages:
1: In open.connection(con, "r") : unable to resolve 'cran.r-project.org'
2: package ‘ppcor’ is not available (for R version 2.15.1)
> library(ppcor)
Error in library(ppcor) : there is no package called ‘ppcor’
> require(ppcor)
Loading required package: ppcor
Warning message:
In library(package, lib.loc = lib.loc, character.only = TRUE,  
logical.return = TRUE,  :
   there is no package called ‘ppcor’

> install.packages("ds")
Warning: unable to access index for repository  
http://cran.fiocruz.br/bin/windows/contrib/2.15
Warning: unable to access index for repository  
http://www.stats.ox.ac.uk/pub/RWin/bin/windows/contrib/2.15
Warning message:
package ‘ds’ is not available (for R version 2.15.1)
> require(ds)
Loading required package: ds
Warning message:
In library(package, lib.loc = lib.loc, character.only = TRUE,  
logical.return = TRUE,  :
   there is no package called ‘ds’

obrigada. An Rocha