[R] a REALLY dumb question

[S Ellison]

> Ok.  I made a copy of the arima.r function called earima.r to put in some print
> statements.  Fair enough.
> 
> Now when I run earima, the .Call statements call find the C subroutines.
> 
> I know that this should be a really simple fix

Not quite simple, as it's a nasty-looking namespace problem. But there IS a work-round using body()<-

First, copy arima from stats to an object in the global namespace; say
earima <- stats:::arima

You can confirm this still works with
> earima(lh, order = c(1,0,0))
 which does exactly the same as 
> arima(lh, order = c(1,0,0))

Now copy the earima body code - the bit between "{...}" in the source, or what you see on the console if you say 
body(earima) - into your code editor. Make your edits to that code, wrap everything (including the {}) in an expression,  and assign that amended expression back into body(earima) using body(earima) <- expression({ revised code here> }).  

Here's what that looks like

> earima <- stats:::arima ## Make the copy

> body(earima)  #Inspect original code 
{
    "%+%" <- function(a, b) .Call(C_TSconv, a, b)
    SSinit <- match.arg(SSinit)
    SS.G <- SSinit == "Gardner1980"
    upARIMA <- function(mod, phi, theta) {
	... ## This is the rest of the body code - don't lose any!
	...
}

#To add a cat() in that, we can do

> body(erima) <- expression({
    cat("Welcome to the new Arima!\n\n")           ### an illustrative cat() welcome call
    "%+%" <- function(a, b) .Call(C_TSconv, a, b)
    SSinit <- match.arg(SSinit)
    SS.G <- SSinit == "Gardner1980"
    upARIMA <- function(mod, phi, theta) {
	...
	...
})

And then 

>  earima(lh, order = c(1,0,0))  #First example from arima

#Returns (or at least displays) ...

Welcome to the new Arima!


Call:
Arima(x = lh, order = c(1, 0, 0))

Coefficients:
         ar1  intercept
      0.5739     2.4133
s.e.  0.1161     0.1466

sigma^2 estimated as 0.1975:  log likelihood = -29.38,  aic = 64.76


... which seems to be doing what you want...


S Ellison




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