[R] exporting long character vectors to dbf

[Prof Brian Ripley]

On Thu, 25 May 2006, Eduardo Leoni wrote:

> I am trying to use RODBC, but still run into some problems. If I
> understood correctly, I have to change the default type for char
> vectors to "text" (or varchar(3000)).

You should do this in sqlSave for the specific table, via the 'typeinfo' 
argument.

> But when I try something like
>
>> library(RODBC)
>> channel <- odbcConnect("supremo", uid="R", case="tolower")
>> setSqlTypeInfo("MySQL",
>               list(double="double",
>                    integer="integer",
>                    character="varchar(3000)",
>                    logical="varchar(5)"))
>
> Warning message:
> number of items to replace is not a multiple of replacement length
>
> I think there is a pair of brackets missing in setSqlTypeInfo here
>   typesR2DBMS[driver] <- value[c("double", "integer", "character",
>       "logical")]

Yes, thank you.

> by the way, is there any easy way to debug packages that does not
> involve reapeatedly modifying, compiling and installing them again??

Not sure what you mean by `debug packages'.  For debugging R code, see the 
section in `Writing R Extension' in R >= 2.3.0

>
>
>
>
>
> On 5/24/06, Prof Brian Ripley <ripley at stats.ox.ac.uk> wrote:
>> On Wed, 24 May 2006, Mulholland, Tom wrote:
>> 
>> > I assume this is (or was) a specification issue. I think write.dbf uses
>> > the shapefile library (C not R library) so it applies to the use of
>> > shapefiles and just happens to have been included in the foreign package
>> > because it has a generic usefullness. (Is that a word?)
>> 
>> Actually, the width of the dbf field comes from the lines in write.dbf:
>>
>>          else if (is.character(x)) {
>>              mf <- max(nchar(x[!is.na(x)]))
>>              precision[i] <- min(max(nlen, mf), 254)
>>              scale[i] <- 0
>> 
>> so that's the limit (254, not 255).  This is stated as a limitation of the
>> dbf format at
>> http://www.clicketyclick.dk/databases/xbase/format/data_types.html
>> so I don't think you can do what you want with .dbf.
>> 
>> > Since I very rarely care about the elegance of my solutions, just that
>> > they work, I would try saving the file in another format that you can
>> > get open office to read and let it do the conversion rather than trying
>> > to get R to do it. I'm sure OpenOffice can deal with straightforward
>> > text files if that's a last resort.
>> 
>> Indeed.  Using an ODBC driver (and RODBC) to write to the database might
>> be a good option.
>> 
>> >
>> > Tom
>> >
>> >> -----Original Message-----
>> >> From: r-help-bounces at stat.math.ethz.ch
>> >> [mailto:r-help-bounces at stat.math.ethz.ch]On Behalf Of Eduardo Leoni
>> >> Sent: Wednesday, 24 May 2006 7:13 AM
>> >> To: r-help at stat.math.ethz.ch
>> >> Subject: [R] exporting long character vectors to dbf
>> >>
>> >>
>> >> Hi -
>> >>
>> >> I need to export data to openoffice base, where one of the elements is
>> >> a long character vector (>255 characters.) write.dbf exports it as
>> >> varchar, truncating the data. Any idea how to do this?
>> >>
>> >> thanks,
>> >>
>> >> -eduardo
>> >>
>> >> ______________________________________________
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>> >>
>> >
>> > ______________________________________________
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>> >
>> 
>> --
>> Brian D. Ripley,                  ripley at stats.ox.ac.uk
>> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
>> University of Oxford,             Tel:  +44 1865 272861 (self)
>> 1 South Parks Road,                     +44 1865 272866 (PA)
>> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>> 
>
>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595