Good example.
The basic problem is in the NAMESPACE file:
importFrom(graphics, plot)
But the version of plot() in the graphics package is not a generic
function. Therefore, when your mpplot() calls it there is no method
dispatch.
You need to import the generic version of plot() from minipkg2 (notice
that there's a message about creating a new generic for plot() when you
install minipkg2).
The line in the NAMESPACE file should be:
importFrom(minipkg2, plot)
In your mini-example, there are some additional steps needed, not
directly related to the problem & possibly not true in the real example.
1. minipkg2 also needs a NAMESPACE, in which it imports from methods
and graphics and exports plot and the class mp2.plot (example attached).
2. Highly recommended though maybe not required here is to use some
form of saved image, e.g. by including "LazyLoad:yes" in the two
DESCRIPTION files.
John
Oosting, J. (PATH) wrote:
I use 2 packages that both implement a S4 plot method, where one package
depends on the other (the bioconductor package globaltest which depends
on multtest). When the plot method is used from within the package, it
seems the default plot method is used, and an error is generated. When
the method is invoked from the console, the plot is created correctly. I
have reproduced this with 2 small packages (minipkg and minipkg2)
implementing just this part.
I've seen a thread about a similar problem, but that seemed mostly due
to already installed packages not handling the new S4 stuff.
mpplot() is a function that creates a class instance and (usually)
invokes the plot immediately. When the dependency on minipkg2 is removed
from the DESCRIPTION file the first call to mpplot() gives no error and
shows the plot.
Jan Oosting
library(minipkg)
Loading required package: minipkg2
Creating a new generic function for 'plot' in 'minipkg2'
mpplot(1:10)
Error in as.vector(x, "double") : cannot coerce to vector
plot(mpplot(1:10,plot=FALSE)) # this shows a proper plot
showMethods("plot")
Function: plot, (package graphics)
x="ANY"
x="mp.plot"
x="mp2.plot"
sessionInfo()
R version 2.4.0 Under development (unstable) (2006-09-04 r39086)
i386-pc-mingw32
locale:
LC_COLLATE=Dutch_Netherlands.1252;LC_CTYPE=Dutch_Netherlands.1252;LC_MON
ETARY=Dutch_Netherlands.1252;LC_NUMERIC=C;LC_TIME=Dutch_Netherlands.1252
attached base packages:
[1] "methods" "stats" "graphics" "grDevices" "utils"
"datasets"
[7] "base"
other attached packages:
minipkg minipkg2
"1.0.0" "1.0.0"
------------------------------------------------------------------------
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import(methods)
importFrom(graphics, plot)
export(plot)
exportClasses("mp2.plot")
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