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




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