[R] read.*: How to read from a URL?
h.wickham at gmail.com
Wed Dec 10 20:40:51 CET 2008
In general, I think you should be able to do:
gimage <- read.jpeg(url(gimageloc))
or alternatively use the EBImage from bioconductor which will read
from a url automatically (it also opens a much wider range of file
img <- readImage(gimageloc, TrueColor)
On Wed, Dec 10, 2008 at 1:17 PM, Michael Friendly <friendly at yorku.ca> wrote:
> 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 distributed
> 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")
> trying URL
> Content type 'image/jpeg' length 35349 bytes (34 Kb)
> opened URL
> downloaded 34 Kb
>  "C:\\DOCUME~1\\default\\LOCALS~1\\Temp\\Rtmp9nNTdV\\file5f906952.jpg"
>> # 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
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