> > On Jan 4, 2016, at 11:17 PM, Lietz, Haiko <haiko.li...@gesis.org> wrote:
> >
> > hi all,
> >
> > when dputting a list of sparse matrices (Matrix package), the output does
> > not contain the data but the information that the list contains sparse
> > matrices.
> >
> > M <- sparseMatrix(i = c(2, 1), j = c(1, 2), x = c(1, 1))
> >
> > dput(M) ... works.
> >
> > dput(list(M, M)) ... does not work.
> >
> > how can I dput a list of sparse matrices?
> > MM <- list(M,M)
> > dput(MM)
> list(<S4 object of class structure("dgCMatrix", package = "Matrix")>,
> <S4 object of class structure("dgCMatrix", package = "Matrix")>)
> No problem.
> I do get an error (clarifying the "did not work" statement), as (perhaps) did
> you?
> > dput(M,M)
> Error in cat("new(\"", clx, "\"\n", file = file, sep = "") :
> invalid connection
> Perhaps the `dput` function was not configured to handle two S4 objects in a
> list?
Indeed. As a matter of fact, a long time I ago I had added a 'FIXME'
comment to the R source code of dput:
see https://svn.r-project.org/R/trunk/src/library/base/R/dput.R
which contains
## FIXME: this should happen in C {deparse2() in ../../../main/deparse.c}
## but we are missing a C-level slotNames()
## Fails e.g. if an S3 list-like object has S4 components
if(isS4(x)) {
clx <- class(x)
cat('new("', clx,'"\n', file = file, sep = "")
for(n in methods::.slotNames(clx)) {
cat(" ,", n, "= ", file = file)
dput(methods::slot(x, n), file = file, control = control)
}
cat(")\n", file = file)
invisible()
}
else .Internal(dput(x, file, opts))
Ideally the above code would be replaced by simply
.Internal(dput(x, file, opts))
and the C code called in do_dput() in
https://svn.r-project.org/R/trunk/src/main/deparse.c
would be improved to do the above in C and be properly
recursive.
(Tested) patches are very welcome!
Martin Maechler,
ETH Zurich and R Core Team
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