R help - Feb 2012 - alternating element in url

Hey everybody, 

it would be really appreciate if you knew the solution to the following
problem. 

I am trying to load data from the internet into R without having to save
them. However, I need to acess a different website for each dataset. So I
want to alternate an element in the URL. Eventually, I want to fill a 3
dimensional matrix/array where each slice is a two-dimensional matrix from
the corresponding website.  For example:

###############################################################################
ID=c(1,5,6,8,10)                      #ID of dataset/website, each dataset
contains a matrix [4x6]
data=array(numeric(0),length(ID) ,4,6)   #empty array [5x4x6]

for (kk in 1:length(ID)) {
url  <-cat("http://ministry.gov/case",ID[kk],"_agencyk") 
#should return
"http://ministry.gov/case1_agencyk" for kk=1, etc.
import.data <-   as.matrix(  read.table(url)  )

for (tt in 1:4) {

for (mm in 1:6) {
data[kk,tt,mm] <- import.data[tt,mm]
}}}
################################################################################

I got all to work, but the problem is assembling the URL.  In the code above
url just returns NULL.  Once that is solved I have trouble because
read.table needs the URL to be in "". If I put
read.table("url") R wont
recognize it as the url I defined earlier. But I also do not know how to use
cat() to get " at beginning and end. 

If I am approaching this in a totally dorky way (likely...), please let me
know, too. 

Thank you!! Frauke

Frauke Hoss
PhD student Carnegie Mellon



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On Feb 6, 2012, at 8:05 PM, frauke wrote:
> Hey everybody,
>
> it would be really appreciate if you knew the solution to the  
> following
> problem.
>
> I am trying to load data from the internet into R without having to  
> save
> them. However, I need to acess a different website for each dataset.  
> So I
> want to alternate an element in the URL. Eventually, I want to fill  
> a 3
> dimensional matrix/array where each slice is a two-dimensional  
> matrix from
> the corresponding website.  For example:
>
>
###############################################################################
> ID=c(1,5,6,8,10)                      #ID of dataset/website, each  
> dataset
> contains a matrix [4x6]
> data=array(numeric(0),length(ID) ,4,6)   #empty array [5x4x6]
?array  ##  with attention to the dim argument
>
> for (kk in 1:length(ID)) {
> url 
<-cat("http://ministry.gov/case",ID[kk],"_agencyk")  
#should
> return
> "http://ministry.gov/case1_agencyk" for kk=1, etc.
> import.data <-   as.matrix(  read.table(url)  )
>
> for (tt in 1:4) {
>
> for (mm in 1:6) {
> data[kk,tt,mm] <- import.data[tt,mm]
> }}}
>
################################################################################
>
> I got all to work, but the problem is assembling the URL.  In the  
> code above
> url just returns NULL.
Right. `cat` always returns NULL. If you want to paste things  
together, then ... use `paste`
>  Once that is solved I have trouble because
> read.table needs the URL to be in "". If I put
read.table("url") R
> wont
> recognize it as the url I defined earlier.
You do not want quotes around url. And its a bad idea to give it the  
name of a function as well. Can't really offer tested code because
http://ministry.gov/case1_agencyk
  doesn't exist.

-- 
David.
> But I also do not know how to use
> cat() to get " at beginning and end.
>
> If I am approaching this in a totally dorky way (likely...), please  
> let me
> know, too.
>
> Thank you!! Frauke
>
> Frauke Hoss
> PhD student Carnegie Mellon
>
>
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/alternating-element-in-url-tp4363423p4363423.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> 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
West Hartford, CT