R help - Oct 2014 - a REALLY dumb question

So please be prepared...

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, but I don't know how.  I do
know that the original arima function is in stats.

Sorry for the trouble.



-- 
Erin Hodgess
Associate Professor
Department of Mathematical and Statistics
University of Houston - Downtown
mailto: erinm.hodgess at gmail.com

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On 03/10/2014 12:09 PM, Erin Hodgess wrote:
> So please be prepared...
>
> 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, but I don't know how. 
I do
> know that the original arima function is in stats.
>
> Sorry for the trouble.
>
>
>
If you run

environment(arima) <- environment(stats::arima)

it should work (assuming your function is still called arima).  The 
problem is that statements like

  .Call(C_ARIMA_Like, y, mod, 0L, TRUE)

refer to variables like C_ARIMA_Like, which are local to the package 
environment of stats.  They aren't exported, so your function (which 
presumably has a different environment) can't see them.

Duncan Murdoch

> 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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