[Rd] (PR#9796) write.dcf/read.dcf cycle converts missing entry

[Bill Dunlap]

On Wed, 18 Jul 2007 ripley at stats.ox.ac.uk wrote:

> I am seeing some problems here, for example when all the fields are
> missing, or all the fields in a row are missing.  I've fixes for those,
> and will commit to R-devel shortly.

write.dcf() is also used by print.packageDesription() so
this change affects how missing fields are printed there.
In 2.5 we got
   > packageDescription("base", fields=c("Version","NoSuchField"))
   Version: 2.5.0
   NoSuchField: NA

   -- File: /dept/devel/sw/R/R.linux.2.5.0/lib/R/library/base/DESCRIPTION
   -- Fields read: Version, NoSuchField
and now it doesn't print anything about the non-existant field
   > packageDescription("base", fields=c("Version","NoSuchField"))
   Version: 2.6.0
   -- File: /homes/bill/R-svn/r-devel/R/library/base/DESCRIPTION
   -- Fields read: Version, NoSuchField
If this isn't acceptable then write.dcf will need a new argument
to control the printing of missing lines.

The missing trailing blank line is an inadvertant change (although
it makes appending fields to a single record dcf file possible).

> > If you read a dcf file with read.dcf(file,fields=c("Field",...))
> > and the file does not contain the desired field "Field",
> > read.dcf puts a character NA for that entry in its output
> > matrix.  If you then call write.dcf, passing it the output
> > of read.dcf(), it will write the entry "Field: NA".  A subsequent
> > read.dcf() on write.dcf's output file will then have a "NA",
> > not a character NA, in the entry for "Field".  I think that
> > write.dcf() should not write lines in the output file where
> > the input matrix contains a character NA.
> > ...
> > The diff would be
> > 19,22c19,24
> > <     eor <- character(nr * nc)
> > <     eor[seq.int(1, nr - 1) * nc] <- "\n"
> > <     writeLines(paste(formatDL(rep.int(colnames(x), nr), c(t(x)),
> > <         style = "list", width = width, indent = indent), eor,
> > ---
> >>     tx <- t(x)
> >>     not.na <- c(!is.na(tx))
> >>     eor <- character(sum(not.na))
> >>     eor[ c(diff(c(col(tx))[not.na]),0)==1 ] <- "\n"
> >>     writeLines(paste(formatDL(rep.int(colnames(x), nr), c(tx),
> >>         style = "list", width = width, indent = indent)[not.na], eor,

   [ The ==1 should be >=1 ]