[R] Write and Load functions from an external file

[Uwe Ligges]

Moumita Das wrote:
> Hi All,
> 
> Would be grateful,if anyone can answer my queries.
> 
> 
> I need to  share code. For example, if I am  working in C/C++, I would put
> some function declarations in .h files that you would include. In PHP, I
> would create files with the common functions in them and then "include()"
> them. So far, I haven't been able to figure out what the standard practice
> is in R.
> 
> 
> 
> The two options are:
> 
> 
> 
> 1. Write everything in one file. No sharing of functions.
> 
> 2. Write libraries - but you *have to package it* first to use it.


What you probably want is 2: Write a *package*. Packaging it does not 
take ages once you have tried it ...

Uwe Ligges


> 
> 
> Neither is a good option. how you I share functions across two scripts?
> 
> 
> 
> there is "source()"
> 
> But are there any other way?
> 
> For example, in python, what I do is create common functions in a separate
> 
> file (say, called A), use those functions from file B by including it like I
> 
> 
> would any other library. Then when I'm ready to 'release' it, I can package
> 
> the library and the script...
> 
> 
> 
> I did find something:-----
> 
> http://www.ma.hw.ac.uk/~stan/R/Rnotes.pdf<http://www.ma.hw.ac.uk/%7Estan/R/Rnotes.pdf>says
> :--
> 
> 
> 
> To create and edit functions, use the (built-in) R function edit. (As usual,
> type ?edit at
> 
> the command prompt for details|see Section 10.)
> 
> Alternatively the function source|also available via the File menu|can be
> used to input
> 
> lengthy function denitions from an externally edited le. (The function dump
> will write an
> 
> existing function denition to a file.)
> 
> But then source() also ,not only loads but parses the file too.
> 
> 
> https://stat.ethz.ch/pipermail/r-help/2007-October/142938.html
> 
> You  can save one or more functions and datasets to a file (see ?save) then
> on starting another session attach that file (see ?attach).
> 
> The process is like:---
> 
> 
> 
> foo <- function(x) mean(as.numeric(x), trim = 0.3)
> 
> save(foo, file = "myproject/rfunctions/saved.rda")
> 
> 
> 
> then, when starting a new session, use
> 
> 
> 
> attach("myproject/rfunctions/saved.rda")
> 
> 
> 
> The .rda extension on the filename is commonly used for saved R data
> 
> sets but you can also have function definitions in a saved file.
> 
> Are these the only ways,and the best ways,to do what I want?
> 
> 
> *--
> Thanks
> Moumita*
>