Thanks for the quick response!

Here is the proper link if you want it.
http://www.spc.noaa.gov/gis/svrgis/zipped/tornado_tracks.zip

Yes, the 2012 tracks have a similar behavior.

One more question...

I tried setting dropNULLGeometries=FALSE but I still seem to only get 
the non null geometries, unless I'm missing something.
Specifically I get:

     > tornados.rg <- readOGR("./SPC_Data/tornado_tracks",
    "tornado_tracks",
    +                         verbose = TRUE,
    +                         p4s=NULL,
    + stringsAsFactors=default.stringsAsFactors(),
    +                         drop_unsupported_fields=FALSE,
    +                         input_field_name_encoding=NULL,
    +                         pointDropZ=FALSE,
    +                         dropNULLGeometries=FALSE,
    +                         useC=FALSE,
    +                         disambiguateFIDs=FALSE,
    +                         addCommentsToPolygons=TRUE)
    OGR data source with driver: ESRI Shapefile
    Source: "./SPC_Data/tornado_tracks", layer: "tornado_tracks"
    with 29806 features and 28 fields
    Feature type: wkbLineString with 2 dimensions
    Warning messages:
    1: In readOGR("./SPC_Data/tornado_tracks", "tornado_tracks", verbose
    = TRUE,  :
       Null geometries found: 147, 427, 542, 730, 739, 851, 859, 1394,
    1422, 1626, 1817, ...
    2: In readOGR("./SPC_Data/tornado_tracks", "tornado_tracks", verbose
    = TRUE,  :
       dropNULLGeometries FALSE, returning only data for null-geometry
    features


The last line states 'returning only data for null-geometry features' so 
I guess the other data simply isn't imported ? Can you confirm that?
If it was loaded into the data frame, I might have a shot at altering 
the ending lat/lon a bit, then somehow rewriting the file.

Another approach I'm taking is to try to produce shapefile from the 
original csv data. If I have luck with that, one option I'll have is to 
alter the ending lat/lon by .01 of a degree, which will be acceptable 
for the work i'm doing. I'm trying QGIS for the latter.


Mark

On 7/31/2013 3:16 PM, Roger Bivand wrote:
> The data you link to are not those you refer to:
>
>> tornados.rg <- readOGR(".", "tornado")
> OGR data source with driver: ESRI Shapefile
> Source: ".", layer: "tornado"
> with 56221 features and 28 fields
> Feature type: wkbPoint with 2 dimensions
>
> that source does not provide any called "tornado_tracks". I do see similar behaviour in:
>
> http://www.spc.noaa.gov/gis/svrgis/zipped/prelim_2012_tornado_tracks.zip
>
> but have no idea whether your analysis applies to this data. Please check and report back. If it does, I can try to see why, but NULL geometries are defined in the OGR shapefile driver, and so by definition have no position data. What you may be seeing as first and last equal coordinates are the entries in the data.frame returned when dropNULLGeometries=FALSE, and may be single point events, which have not been given a geometry. You would need to find out from the data provider what they meant by this. It is not permitted to mix geometry types in a shapefile, so the problem may arise if they try to do so; the shapefile contains invalid geometry types for the NULL geometries, suggesting that they are not read or set correctly. The event_id values should permit them to be identified.
>
> Hope this helps,
>
> Roger
>
>
> --
> Roger Bivand
> NHH Norwegian School of Economics
> Helleveien 30, 5045 Bergen, Norway
> Roger.Bivand@nhh.no
>
>
> ________________________________________
> Fra: r-sig-geo-bounces@r-project.org [r-sig-geo-bounces@r-project.org] p&#229; vegne av Mark Gibbas [mark@weather-source.com]
> Sendt: 31. juli 2013 7:17
> Til: r-sig-geo@r-project.org
> Emne: [R-sig-Geo] readOGR -- Dropping null geometries -- Possible issue with path as a point
>
> Greetings!
>
> I am attempting to read a shapefile with readOGR and I'm getting the
> message 'Dropping null geometries'. From what I have been able to
> discern the null geometries seem to be associated with lines where the
> begin and end lat/lon are the same. So effectively the line is really
> just a point. Should such a case cause readOGR to treat this as a null
> geometry? Or is it possible something else is happening? Any insight
> into this is _very_ appreciated. Thanks!
>
> ###############
> # DATA DOWNLOAD
>
>      http://www.spc.noaa.gov/gis/svrgis/zipped/tornado.zip
>
> ###############
> # SAMPLE CODE
>
>      setwd("C:/Users/mark/Downloads/GIS_Data")
>      library(rgdal)
>      tornados.rg <- readOGR("./SPC_Data/tornado_tracks", "tornado_tracks")
>
> ###############
> # RESULTS
>
>      OGR data source with driver: ESRI Shapefile
>      Source: "./SPC_Data/tornado_tracks", layer: "tornado_tracks"
>      with 29806 features and 28 fields
>      Feature type: wkbLineString with 2 dimensions
>      Warning message:
>      In readOGR("./SPC_Data/tornado_tracks", "tornado_tracks") :
>         Dropping null geometries: 147, 427, 542, 730, 739, 851, 859, ...
>
> ###############
> # INVESTIGATION
>
>      By comparing the elements of what was read by readOGR to a CSV file
>      of the same data, I find that the ones skipped by readOGR are
>      elements where the begin and end lat/lon are the same.
>
> ###############
> # SESSION INFO
>
>       > sessionInfo()
>      R version 2.15.3 (2013-03-01)
>      Platform: x86_64-w64-mingw32/x64 (64-bit)
>
>      locale:
>      [1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United
>      States.1252    LC_MONETARY=English_United States.1252 LC_NUMERIC=C
>      [5] LC_TIME=English_United States.1252
>
>      attached base packages:
>      [1] grid      stats     graphics  grDevices utils     datasets
>      methods   base
>
>      other attached packages:
>      [1] PBSmapping_2.66.53 maptools_0.8-25    lattice_0.20-13
>      foreign_0.8-52     rgeos_0.2-19       rgdal_0.8-10 sp_1.0-11
>
>      loaded via a namespace (and not attached):
>      [1] tools_2.15.3
>
>
>
>
>          [[alternative HTML version deleted]]
>
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> R-sig-Geo@r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>


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