[R-sig-Geo] write/readOGR issue with date / time strings

[Roger Bivand]

On Fri, 11 Nov 2011, Corrie Curtice wrote:

> Hello,
>
> Apologies if this has already been addressed somewhere, I did a brief search
> of archives but didn't find quite this issue.

Which versions of what are you using? You should provide the output of 
sessionInfo(), the messages given when rgdal loads, and details of how you 
installed rgdal. In addition, a use case would be helpful, but only when 
we know what version you are using. In current rgdal, data frame columns 
of class POSIXt are converted to character strings before writing with 
writeOGR().

Roger

>
> I'm writing out an ESRI shapefile.  My spdf has a date/time field.  Looks
> like this:
>
>> head(spdfUTM at data)
>           krillGMTtime          Lat          Lon
> 1   2010-05-12 12:34:21 -64.67655969 -62.15040195
> 21  2010-05-12 12:35:12  -64.6771229  -62.1519511
> 38  2010-05-12 12:36:02 -64.67775863 -62.15340614
> 57  2010-05-12 12:36:53 -64.67838269 -62.15494829
> 78  2010-05-12 12:37:43 -64.67901497 -62.15647203
> 100 2010-05-12 12:38:37 -64.67973667 -62.15773224
>
> All three fields are reported to be "factors" by str.  writeOGR appears
> happy:
>
>> writeOGR(spdfUTM,dd,layer="krillPoints-UTM",driver="ESRI
> Shapefile",verbose=TRUE,overwrite=TRUE)
> $object_type
> [1] "SpatialPointsDataFrame"
> $output_dsn
> [1] "/users/corriecurtice/documents/Data_2010/Shapefiles/"
> $output_layer
> [1] "krillPoints-UTM"
> $output_diver
> [1] "ESRI Shapefile"
> $output_n
> [1] 11179
> $output_nfields
> [1] 3
> $output_fields
> [1] "krillGMTtime" "Lat"          "Lon"
> $output_fclasses
> [1] 4 4 4
> $dataset_options
> NULL
> $layer_options
> NULL
> Warning message:
> In writeOGR(spdfUTM, dd, layer = "krillPoints-UTM", driver = "ESRI
> Shapefile",  :
>  existing layer removed
>
> When I read it right back in again, the date/time field is NAs.  This is
> also true if I load the shapefile into ArcMap.
>
>> foo <- readOGR(dd,layer="krillPoints-UTM",verbose=TRUE)
> OGR data source with driver: ESRI Shapefile
> Source: "/users/corriecurtice/documents/Data_2010/Shapefiles/", layer:
> "krillPoints-UTM"
> with 11179 features and 3 fields
> Feature type: wkbPoint with 2 dimensions
>
>> head(foo at data)
>  krillGMTti          Lat          Lon
> 1       <NA> -64.67655969 -62.15040195
> 2       <NA>  -64.6771229  -62.1519511
> 3       <NA> -64.67775863 -62.15340614
> 4       <NA> -64.67838269 -62.15494829
> 5       <NA> -64.67901497 -62.15647203
> 6       <NA> -64.67973667 -62.15773224
>
> Thoughts? Am I missing something obvious?
>
> I can break it up into separate date and time fields, but since the field is
> simply a factor anyways I'm not sure how that would help.
>
> Cheers,
>
> Corrie
>
> ---
> Corrie Curtice
> Research Analyst
> Marine Geospatial Ecology Lab
> Nicholas School of the Environment, Duke University
> http://mgel.env.duke.edu
> em: corrie.curtice at duke.edu
> ph: 252-504-7538
>
>
>
>
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>
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-- 
Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no