[R-pkg-devel] Mysterious "invalid z limit"

[Kevin R. Coombes]

Hi,

I am in the middle of developing a new package, which contains a 
markdown-knitr-html vignette. When I try to run

R CMD build [mypackagedirectory]

I get an error message

Quitting from lines 330-336
Error: processing vignette  failed with diagnostics:
invalid z limits

If I run the same markdown script interactively inside R Studio, there 
is no error.
If I knit the markdown script inside R Studio, it produces the correct 
HTML output, with no error.

The offending lines of code (the chunk at 330-336) invoke an "image" 
method on an object of a class defined in the package, which in turn 
computes a matrix from items inside the object and calls image.default, 
which is presumably where the error is coming from.

Two questions: (1) How is it possible that the same code works error 
free in the RStudio contexts, but fails in the attempt to build the package?
(2) Any suggestions on how to debug something that only throws an error 
from "R CMD build" would be most welcome.

Thanks in advance,
   Kevin