On 03.01.2012 07:50, Rolf Turner wrote:
On 03/01/12 17:02, Li SUN wrote:
Hello,
I am a beginner to the R language and find it fantastic and
well-designed, quite different from other programming languages.
What a refreshingly sensible attitude!!! :-)
This is the first time I post on the r-help mailing list.
In invoking the function source(filename), it seems that the filename
has to exist in the current working directory, otherwise it has to be
specified in full path.
No: relative (to the working directory) specifications are possible as well.
Uwe Ligges
So is there any mechanism(such as environment
variable) to specify an additional directory of .R files that source()
could search in?
I'm no expert on this, and others may correct me, but
(1) I don't believe any such mechanism exists.
(2) It's probably not a good idea, even if such a mechanism
were to exist. Directories have a tree structure, rather than
being linearly ordered in the way that data bases on your
R search path are ordered.
I believe you would run all sorts of risks of confusion and
of getting the wrong file were you to invoke such a mechanism.
It is ``good practice'' to have separate directories associated
with different projects and to situate all files, that you might wish
to source in respect of a given project, in the directory associated
with that project.
I know that this is an irritating sort of response --- ``No, you can't
do that, and you shouldn't do it anyway!'' --- but I sincerely believe
this to be true.
That being said, I also believe that you could program up such a mechanism
yourself. I.e. build a function "source2()" which would have a "hard
coded" list
of directories to search, and would make use of the "try()" function.
Might be a good exercise for you, given that you are starting out in R
and looking to upgrade your skills! :-)
cheers,
Rolf Turner
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