[R] readJPEG function cannot open jpeg files

[Prof Brian Ripley]

On 14/01/2013 16:26, Suzen, Mehmet wrote:
> Similar issue with URLs:

Not a similar issue at all: a URL is not a file.  That most functions in 
R itself open connections including URLs does not mean that contributed 
packages do.  The package help is quite specific about its requirements.

   source: Either name of the file to read from or a raw vector
           representing the JPEG file content.

Which suggests to you how you can do this, apart from download.file, of 
course.  Something like

readJPEG(readBin(yesWeCan, "raw", 1e6))

>
>> yesWeCan <- "http://upload.wikimedia.org/wikipedia/commons/9/9d/Barack_Obama.jpg"
>> url(yesWeCan)
>                                                            description
> "http://upload.wikimedia.org/wikipedia/commons/9/9d/Barack_Obama.jpg"
>                                                                  class
>                                                                  "url"
>                                                                   mode
>                                                                    "r"
>                                                                   text
>                                                                 "text"
>                                                                 opened
>                                                               "closed"
>                                                               can read
>                                                                  "yes"
>                                                              can write
>                                                                   "no"
>> readJPEG(yesWeCan)
> Error in readJPEG(yesWeCan) :
>    unable to open
> http://upload.wikimedia.org/wikipedia/commons/9/9d/Barack_Obama.jpg
>
>
> On 14 January 2013 14:57, Yi Yuan <lambandme at gmail.com> wrote:
>> I installed jpeg package and tried to use
>>
>>   kim<-readJPEG("kim.jpeg") to read in a jpeg file, but R gave me an error:
>> Error in readJPEG("kim.jpeg") : unable to open kim.jpeg
>>
>> I already put "kim.jpeg" in Rstudio's default working directory: "E:\home
>> work\Rstudio". So I don't think it's a problem caused by omitting the file's
>> path. But I tried with the full path version just in case and still got the
>> "unable to open" error:
>>
>> kim<-readJPEG("E:\\ home work\\Rstudio\\kim.jpeg")
>> Error in readJPEG("E:\\ home work\\Rstudio\\kim.jpeg") :
>>    unable to open E:\ home work\Rstudio\kim.jpeg
>>
>> So now I really don't know what is wrong.
>>
>>          [[alternative HTML version deleted]]
>>
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>> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> 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.
>


-- 
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