[R-SIG-Mac] Mac-only problem using readOGR(), which uses ogrInfo(), to read a shapefile from a directory on a USB pen drive

[Ken Beath]

My thought is that it might be that USB drives are usually MSDOS formatted. Usually not a problem but rgdal works with directories. Formatting  in a Mac with Disk Utility might be a work-around, with the limitation that the USB will only work in Macs.

I would also try verbose=TRUE which may give more information.

In the absence of other ideas contacting the package author can help.

Ken

> On 4 Mar 2017, at 3:32 am, D G. Rossiter <d.g.rossiter at cornell.edu> wrote:
> 
> I ran across a Mac-only problem using readOGR(), which uses ogrInfo(), to read a shapefile from a directory on a USB pen drive. I tested the behaviour on a Windows 10 machine and did not get the problem. 
> 
> Trying to read from the USB drive, with relative and full paths:
> 
>> setwd("/Volumes/ISPRS/“) # this is my connected USB drive
>> list.files()     
> [1] "map7100.dbf"                      "map7100.prj"                     
> [3] "map7100.sbn"                      "map7100.sbx"                     
> [5] "map7100.shp"                      "map7100.shp.xml"                 
> [7] "map7100.shx"  
>> file.exists("map7100.shp")
> [1] TRUE
>> usa <- readOGR(dsn=".", layer="map7100")
> Error in ogrInfo(dsn = dsn, layer = layer, encoding = encoding, use_iconv = use_iconv,  : 
>  Cannot open data source
>> usa <- readOGR(dsn="/Volumes/ISPRS", layer="map7100")
> Error in ogrInfo(dsn = dsn, layer = layer, encoding = encoding, use_iconv = use_iconv,  : 
>  Cannot open data source
> 
> But, readOGR reads the shapefile correctly if it’s located on the Mac’s internal drive:
> 
>> setwd("/Users/rossiter/data/edu/dgeostats/ex")
>> file.exists("./ds/NEweather/map7100.shp")
> [1] TRUE
>> usa <- readOGR(dsn="./ds/NEweather", layer="map7100")
> OGR data source with driver: ESRI Shapefile 
> Source: "./ds/NEweather", layer: "map7100"
> with 7926 features
> It has 19 fields
> 
> All packages are up to date. Here is the sessionInfo():
> 
> R version 3.3.2 (2016-10-31)
> Platform: x86_64-apple-darwin13.4.0 (64-bit)
> Running under: OS X El Capitan 10.11.6
> 
> locale:
> [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
> 
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base     
> 
> other attached packages:
> [1] ggplot2_2.2.1  sf_0.3-4       maptools_0.9-1 rgdal_1.2-5   
> [5] sp_1.2-4       gstat_1.1-4   
> 
> loaded via a namespace (and not attached):
> [1] Rcpp_0.12.9      plyr_1.8.4       xts_0.9-7        tools_3.3.2     
> [5] digest_0.6.12    evaluate_0.10    tibble_1.2       gtable_0.2.0    
> [9] lattice_0.20-34  DBI_0.5-1        yaml_2.1.14      stringr_1.2.0   
> [13] knitr_1.15.1     rprojroot_1.2    grid_3.3.2       spacetime_1.2-0 
> [17] foreign_0.8-67   rmarkdown_1.3    udunits2_0.13    magrittr_1.5    
> [21] backports_1.0.5  scales_0.4.1     intervals_0.15.1 htmltools_0.3.5 
> [25] units_0.4-2      rsconnect_0.7    assertthat_0.1   colorspace_1.3-2
> [29] labeling_0.3     stringi_1.1.2    lazyeval_0.2.0   munsell_0.4.3   
> [33] FNN_1.1          zoo_1.7-14  
> 
> This is a problem because several of my students have OS/X machines and like to work from USB-connected external drives.
> 
> D G (David) Rossiter
> Section of Soil & Crop Sciences
> Cornell University
> http://www.css.cornell.edu/faculty/dgr2/
> 
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