[R] can I call user-created functions without source() ?

[Duncan Murdoch]

Just a few comments below on alternative ways to do the same things:

On 6/19/2006 8:19 AM, Joerg van den Hoff wrote:

> for short term usage of some specialized functions I have added some 
> lines to the `.Rprofile' in my home(!) directory as follows (probably 
> there are smarter solutions, but at least it works):
> 
> #source some temporary useful functions:
> fl <- dir(path='~/rfiles/current',patt='.*\\.R$',full.names=TRUE)
> for (i in fl) {cat(paste('source("',i,'")\n',sep="")); source(i)}
> rm(i,fl)

Another way to do this without worrying about overwriting some existing 
variables is

local({
fl <- ...
for (i in fl) ...
})

No need to remove fl and i at the end; they were created in a temporary 
environment, which was deleted at the end.

> 
> here, I have put all the temporary stuff in a single dedicated dir 
> `~/rfiles/current', but of course you can use several dirs in this way. 
> all files in this dir with names ending in `.R' are sourced on startup 
> of R. this roughly works like one of the directories on MATLAB's search 
> path: every function definition in this directory is  'understood' by R 
> (but everything is loaded into the workspace on startup, no matter, 
> whether you really need it in the end: no real `load on demand'). 

It's possible to have load on demand in R, and this is used in packages. 
  It's probably not worth the trouble to use it unless you're using a 
package.


one
> important difference, though: this is only sensible for function 
> definitions, not scripts ('executable programms' (which would directly 
> be executed on R startup, otherwise).
> and, contrary to matlab/octave, this is not dynamic: everything is read 
> in at startup, later modifications to the directories are not recognized 
> without explicitely sourcing the files again.

There isn't really any reasonable way around this.  I suppose some hook 
could be created to automatically read the file if the time stamp 
changes, but that's not really the R way of doing things:  generally in 
R active things are in the workspace, not on disk.  A good way to work 
is prepare things on disk, then when they are ready, explicitly import 
them into R.

> 
> if you in addition you want to load definitions from the startup 
> directory where you launch R (your project dir), the above could be 
> modified to:
> 
> #source some temporary useful functions from startup dir:
> fl <- dir(path=getwd(),patt='.*\\.R$',full.names=TRUE)
> for (i in fl) {cat(paste('source("',i,'")\n',sep="")); source(i)}
> rm(i,fl)
> 
> in this way you at least don't need a separate `.Rprofile' in each 
> project dir.

Another alternative if you want something special in the project is to 
create a .Rprofile file there, and put source("~/.Rprofile") into it, so 
both the local changes and the general ones get loaded.

Duncan Murdoch
> 
> 
> 
> joerg
> 
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