[Rd] Bug in print.Arima and patch

[Prof Brian Ripley]

Why not use NROW?

On Fri, 5 Jun 2009, Gavin Simpson wrote:

> Dear List,
>
> A posting to R-Help exposed this problem with the print method for
> objects of class Arima:
>
>> set.seed(1)
>> x <- arima.sim(n = 100, list(ar = 0.8897, ma = -0.2279))
>> mod <- arima(x, order = c(1,0,1))
>> coefs <- coef(mod)
>> mod2 <- arima(x, order = c(1,0,1), fixed = coefs)
>> mod2
>
> Call:
> arima(x = x, order = c(1, 0, 1), fixed = coefs)
>
> Coefficients:
> Error in se && nrow(x$var.coef) : invalid 'y' type in 'x && y'
>> print(mod2, se = FALSE)
>
> Call:
> arima(x = x, order = c(1, 0, 1), fixed = coefs)
>
> Coefficients:
>      ar1        ma1  intercept
>   0.9323    -0.2940    -0.0353
>
> sigma^2 estimated as 0.8339:  log likelihood = -133.55,  aic = 269.11
>
> The print methods raises an error in this case, where all coefficients
> are fixed, because x$var.coef is of length(0), which in turn results in
> NULL being used in the && comparison, resulting in the error.
>
> A potential fix is to just include a check for length(x$var.coef) > 0 in
> the if statement. This fix, when applied to:
>
> R version 2.10.0 Under development (unstable) (2009-06-05 r48712)
>
> fixes this particular problem and passes make check-devel. A patch
> against r48712 is attached, and included here in-line:
>
> [gavin at desktop build]$ svn diff ../src/library/stats/R/arima.R
> Index: ../src/library/stats/R/arima.R
> ===================================================================
> --- ../src/library/stats/R/arima.R	(revision 48712)
> +++ ../src/library/stats/R/arima.R	(working copy)
> @@ -355,7 +355,7 @@
>     if (length(x$coef)) {
>         cat("Coefficients:\n")
>         coef <- round(x$coef, digits = digits)
> -        if (se && nrow(x$var.coef)) {
> +        if (se && length(x$var.coef) > 0 && nrow(x$var.coef)) {
>             ses <- rep(0, length(coef))
>             ses[x$mask] <- round(sqrt(diag(x$var.coef)), digits = digits)
>             coef <- matrix(coef, 1L, dimnames = list(NULL, names(coef)))
>
> HTH
>
> G
> -- 
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> Dr. Gavin Simpson             [t] +44 (0)20 7679 0522
> ECRC, UCL Geography,          [f] +44 (0)20 7679 0565
> Pearson Building,             [e] gavin.simpsonATNOSPAMucl.ac.uk
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>
>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595