R help - Sep 2004 - Confused about loading other packages from a package

In my package, I create a new method for plot with the following signature:

setMethod("plot", signature(x="marrayNorm",
y="formula"), plot.ma)

where marrayNorm is a class defined in the marray package.   After
building and installing my package, I get the following warnings when
I load my package (with library(maVis)):

Warning messages: 
1: In the method signature for function "plot", class
"marrayRaw" has
no current definition in: matchSignature(signature, fdef, where)
2: In the method signature for function "plot", class
"marrayRaw" has
no current definition in: matchSignature(signature, fdef, where)

(but everything appears to work ok regardless).  I have tried
require(marray) both inside and outside of the .onLoad method.

I presume this is a caused by some difference in require depending on
whether or not it is within a package or not, as simply source()ing
the code gives no errors.  What should I do?  Ignore the warnings (or
turn them off somehow?) or use a different method of loading marray?
I'm also a bit confused about what is best practice for calling
methods in other packages - use namespace:::, use require, use
library, use the depends field in DESCRIPTION, so any advice here
would also be appreciated.

Thanks for you help,

Hadley

In R 2.0.0-to-be I think putting marray in the Depends: field will 
solve your problem.  Otherwise, you might want to import the 
"marrayNorm" class in your NAMESPACE file.

-roger

hadley wickham wrote:
> In my package, I create a new method for plot with the following signature:
> 
> setMethod("plot", signature(x="marrayNorm",
y="formula"), plot.ma)
> 
> where marrayNorm is a class defined in the marray package.   After
> building and installing my package, I get the following warnings when
> I load my package (with library(maVis)):
> 
> Warning messages: 
> 1: In the method signature for function "plot", class
"marrayRaw" has
> no current definition in: matchSignature(signature, fdef, where)
> 2: In the method signature for function "plot", class
"marrayRaw" has
> no current definition in: matchSignature(signature, fdef, where)
> 
> (but everything appears to work ok regardless).  I have tried
> require(marray) both inside and outside of the .onLoad method.
> 
> I presume this is a caused by some difference in require depending on
> whether or not it is within a package or not, as simply source()ing
> the code gives no errors.  What should I do?  Ignore the warnings (or
> turn them off somehow?) or use a different method of loading marray?
> I'm also a bit confused about what is best practice for calling
> methods in other packages - use namespace:::, use require, use
> library, use the depends field in DESCRIPTION, so any advice here
> would also be appreciated.
> 
> Thanks for you help,
> 
> Hadley
> 
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