From ripley@stats.ox.ac.uk  Tue Nov 30 14:16:55 1999
From: ripley@stats.ox.ac.uk (ripley@stats.ox.ac.uk)
Date: Tue, 30 Nov 1999 15:16:55 +0100 (MET)
Subject: image stops detecting wrong sized z matrix (PR#352)
Message-ID: <199911301416.PAA29330@pubhealth.ku.dk>

[...]

> This is where example(krige) from library(sgeostat) stops with R 0.90.0:
> 
> krige> image(grid$x, grid$y, grid$krige$zhat, add = T)
> Error in length(x) == nrow(z) : comparison (1) is possible only for vector
> types
> 
> in previous versions of R the above image() call worked, because image()
> did the transformation 
> 
>   grid$krige$zhat -> matrix(grid$krige$zhat,length(grid$x),length(grid$x))
> 
> iself. (BTW, contour() didn't)

(In fact, it just ignored dim(z) which therefore could be null.)

> Was this change of behaviour in image() made intentionally? 

Yes, to allow a more general specification of x and y, for S compatibility
(and general usefulness!).


I believe this is a bug in sgeostat not in R: it has long been
documented that z should be a matrix. What has happened is that we
now make use of the documented behaviour.  Suppose z were of length 90,
and each of x and y were of length 10. That is now ambiguous (and BTW,
just gave the wrong plot in 0.65.1, something that has caught me
more than once).

I will add a more specific error message testing that z is a matrix.


-- 
Brian D. Ripley,                  ripley@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 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595


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image stops detecting wrong sized z matrix (PR#352)
ripley@stats.ox.ac.uk