[R] read.*: How to read from a URL?
friendly at yorku.ca
Wed Dec 10 20:17:06 CET 2008
The question is how to use a URL in place of a file= argument for
read.*.functions that do
not support this internally.
e.g., utils::read.table() and her family all support a file= argument
that can take a URL
equally well as a local file. So, if I have a file on the web, I can
equally well do
> langren <- read.csv("langrens.csv", header=TRUE)
> langren <-
where the latter is more convenient for posts to this list or
rimage::read.jpeg() doesn't support URLs, and the only way I've found is
to download the
image file from a URL to a temp file, in several steps.
This is probably a more general problem than just read.jpeg,
so maybe there is a general idiom for this case, or better-- other
read.* functions could
be encouraged to support URLs.
> # local file: OK
> gimage <-
> gimageloc <-
> dest <- paste(tempfile(),'.jpg', sep='')
> download.file(gimageloc, dest, mode="wb")
Content type 'image/jpeg' length 35349 bytes (34 Kb)
downloaded 34 Kb
> # Is there something simpler??
> gimage <- read.jpeg(dest)
> # I thought file() might work, but evidently not.
> gimage <- read.jpeg(file(gimageloc))
Error in read.jpeg(file(gimageloc)) : Can't open file.
Michael Friendly Email: friendly AT yorku DOT ca
Professor, Psychology Dept.
York University Voice: 416 736-5115 x66249 Fax: 416 736-5814
4700 Keele Street http://www.math.yorku.ca/SCS/friendly.html
Toronto, ONT M3J 1P3 CANADA
More information about the R-help