problems with download.file() from ftp?

Hi Zack,

  You might explore some of the options of libcurl
via the RCurl package for R. Depending on the server,
you may want to send either EPSV or PASV commands at
some point in the dialog.

libcurl, and the functions in RCurl, give you a great
deal of control in cutomizing and controlling the
requests to the FTP/HTTP/... server, while the
functions in base R are less flexible.

 D.


zack holden wrote:

Professor Ripley and Brian Rowe,
Thank you both for your helpful suggestions. I was unable to solve 
this problem. Apparently there is a passive FTP server that is not 
supported by R. I'll have to find another programming language, 
perhaps IDL, that can do this. Manually retrieving the hundreds of 
files I need is not an option.  
thank you again for your attempts to help me.  
Best regards,
Zack

Date: Mon, 12 Jan 2009 16:37:43 +0000
From: ripley at stats.ox.ac.uk
To: zack_holden at hotmail.com
CC: r-help at r-project.org
Subject: Re: [R] problems with download.file() from ftp?

First, try the example in the test file (tests/internet.R)

read.table("ftp://ftp.stats.ox.ac.uk/pub/datasets/csb/ch11b.dat")

or

download.file("ftp://ftp.stats.ox.ac.uk/pub/datasets/csb/ch11b.dat", 
"test"

That is known to work on many, many R systems.

I get the same error as you on that URL, but it looks to me that the 
site required PASV ftp, something R's download.file does not support. 
From the detailed logs (options(internet.info=0)

<<<
230---------------------------------------------------------
230- Welcome To The
230- Natural Resources Conservation Service - USDA
230- NATIONAL WATER and CLIMATE CENTER
230---------------------------------------------------------
230-
230- The Local Date and Time is Mon Jan 12 08:30:25 2009
230- Current Directory is /
230- Information Contact is: info at wcc.nrcs.usda.gov
230- -----------------------------------------------------------
230- Note that data files herein are at most updated once an hour.
230-
230 Guest login ok, access restrictions apply.

-- 
19: In download.file(url, dest) :
---

-- 
20: In download.file(url, dest) : Got 230
21: In download.file(url, dest) : Invalid answer to PASV

Since you are on Windows, using --internet2 (see the rw-FAQ) might work.

On Mon, 12 Jan 2009, zack holden wrote:

Dear list,

I am trying to download a text file from an ftp site using 
download.file().

I used the following code:
url <- 
"ftp://ftp.wcc.nrcs.usda.gov/data/snow/snow_course/table/history/idaho/13e19.txt" 

dest <- "c:/test/downloadtest.txt"
download.file(url, dest)
I get this error message, indicating that R is unable to open the 
connection:
trying URL 
'ftp://ftp.wcc.nrcs.usda.gov/data/snow/snow_course/table/history/idaho/13e19.txt' 

Error in download.file(url, dest) :
cannot open URL 
'ftp://ftp.wcc.nrcs.usda.gov/data/snow/snow_course/table/history/idaho/13e19.txt' 


I'm sure there is a simple solution that allows R to open this 
connection, but after reading the "url" help file for an hour, I 
can't seem to find the solution. Is anyone willing to help me solve 
this problem?

thanks in advance for any advice,

Zack

-- 
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