[R-sig-Geo] Issues with a GDB file in R?

Aguirre Perez, Roman r@454 @ending from exeter@@c@uk
Mon May 7 13:28:50 CEST 2018



On 07/05/2018, 08:36, "Roger Bivand" <Roger.Bivand at nhh.no> wrote:

    On Sun, 6 May 2018, Aguirre Perez, Roman wrote:
    
    > On 05/05/2018, 12:03, "Roger Bivand" <Roger.Bivand at nhh.no> wrote:
    >
    >    On Fri, 4 May 2018, Roger Bivand wrote:
    >
    >    > On Thu, 3 May 2018, Roger Bivand wrote:
    >    >
    >    >>  On Thu, 3 May 2018, Aguirre Perez, Roman wrote:
    >    >>
    >    >>>   Hi again,
    >    >>>
    >    >>>   first of all, thanks a lot for your comments. It's becoming quite
    >    >>>   interesting how to perform this task with such amount of data.
    >    >>>
    >    >>>
    >    >>>   Here is an update...
    >    >>>
    >    >>>   Cotton, I could read the geodatabase by using the commands I shared.
    >    >>>   However, my R session crashed after overlaying it with a small set of
    >    >>>   polygons. I guess it was because the size of the sp object (around 14.5
    >    >>>   GB). It's also worth mentioning that it was just a "multipolygon" (is
    >    >>>   that
    >    >>>   the correct word?) formed by 2370829 polygons. I haven’t succeeded on
    >    >>>   installing the sf package, but I will keep trying it.
    >    >>>
    >    >>>   Melanie, I already downloaded and read the geoTiff version. At first
    >    >>>   sight, it seems that this object doesn’t have enough features as to
    >    >>>   perform the overlying. I might have a biased idea of how raster objects
    >    >>>   work - I'm too stick to the representation of shapefiles which sounds
    >    >>>   quite related with Roger's idea. So I will start to explore it in order
    >    >>>   to
    >    >>>   gain a bit more understanding on it.
    >    >>>
    >    >>>   Roger, I certainly need to know which category is associated with each
    >    >>>   CLC
    >    >>>   polygon in order to compute the area covered by each of these classes
    >    >>>   within each NUTS3 region. Therefore, I still need to use a vector-vector
    >    >>>   overlay, right?
    >    >>
    >    >>  On the contrary. The geoTiffs are coded as described in the documentation.
    >    >>  Your output is simply the count of raster cells by NUTS3 for each of the
    >    >>  categories. The geoTiff is in ETRS_1989_LAEA, so is projected; it includes
    >    >>  a lot of sea and no data because of the French overseas territories.
    >    >>
    >    >>  You could possibly use PostGIS to do the intersections, or use GRASS for
    >    >>  raster-vector counts (say through rgrass7). In R, you would want to add a
    >    >>  NUTS3 ID band to the land cover raster, then aggregate by NUTS3 ID.
    >    >>
    >    >>  I would suggest using GRASS as the most obvious route, reading the raster,
    >    >>  reading the NUTS3 boundaries into a separate location, projecting to LAEA,
    >    >>  then rasterising the NUTS3 regions (v.to.rast) and running r.cross. You
    >    >>  get 32K output categories, the 48 corine categories times the count of
    >    >>  NUTS3 regions minus the nulls (there aren't many glaciers in most
    >    >>  regions). You'll then need to match back the Corine codes and the NUTS3
    >    >>  codes - see in the category label file shown by r.category.
    >    >>
    >    >>  I'll try to provide code tomorrow.
    >    >
    >    > Combining R and GRASS seems to work, but no guarantees.
    >    >
    >    > library(sp)
    >    > library(rgdal)
    >    > Gi <- GDALinfo("g250_clc12_V18_5.tif")
    >    > makeSG <- function(x) {
    >    >   stopifnot(class(x) == "GDALobj")
    >    >   p4 <- attr(x, "projection")
    >    >   gt <- GridTopology(c(x[4]+(x[6]/2), x[5]+(x[7]/2)), c(x[6], x[7]),
    >    >     c(x[2], x[1]))
    >    >  SpatialGrid(gt, CRS(p4))
    >    > }
    >    > SG <- makeSG(Gi)
    >    > nuts_ll <- readOGR("NUTS_RG_01M_2013_4326_LEVL_3.shp")
    >    > nuts_laea <- spTransform(nuts_ll, CRS(attr(Gi, "projection")))
    >    > library(rgrass7)
    >    > td <- tempdir()
    >    > iG <- initGRASS("/home/rsb/topics/grass/g740/grass-7.4.0", td, SG)
    >    > # your GRASS will be where you installed it
    >    > writeVECT(nuts_laea, "nuts", v.in.ogr_flags="o")
    >    > execGRASS("r.in.gdal", input="g250_clc12_V18_5.tif", output="corine",
    >    >  flags="o")
    >    > execGRASS("v.to.rast", input="nuts", output="nuts3", use="cat",
    >    >  label_column="FID")
    >    > execGRASS("r.cross", input="nuts3,corine", output="cross_nuts3")
    >    > r_stats0 <- execGRASS("r.stats", input="cross_nuts3", flags="a",
    >    >  intern=TRUE)
    >    > r_stats1 <- gsub("\\*", "NA", r_stats0)
    >    > con_stats <- textConnection(r_stats1)
    >    > stats <- read.table(con_stats, header=FALSE, col.names=c("cross_cat",
    >    >  "area"), colClasses=c("integer", "numeric"))
    >    > close(con_stats)
    >    > r_cats0 <- execGRASS("r.category", map="cross_nuts3", intern=TRUE)
    >    > r_cats1 <- gsub(";", "", r_cats0)
    >    > r_cats2 <- gsub("\t", " ", r_cats1)
    >    > r_cats3 <- gsub("no data", "no_data", r_cats2)
    >    > r_cats4 <- gsub("category ", "", r_cats3)
    >    > r_cats4[1] <- paste0(r_cats4[1], "NA NA")
    >    > r_cats_split <- strsplit(r_cats4, " ")
    >    > cats <- data.frame(cross_cat=as.integer(sapply(r_cats_split, "[", 1)),
    >    >   nuts=sapply(r_cats_split, "[", 2),
    >    >   corine=as.integer(sapply(r_cats_split, "[", 3)))
    >    > catstats <- merge(cats, stats, by="cross_cat", all=TRUE)
    >    > agg_areas <- tapply(catstats$area, list(catstats$nuts, catstats$corine),
    >    >  sum)
    >    > library(foreign)
    >    > corine_labels <- read.dbf("g250_clc12_V18_5.tif.vat.dbf", as.is=TRUE)
    >    > o <- match(colnames(agg_areas), as.character(corine_labels$Value))
    >    > colnames(agg_areas) <- corine_labels$LABEL3[o]
    >    > agg_areas_df <- as.data.frame(agg_areas)
    >    > agg_areas_df1 <- agg_areas_df[-which(!(row.names(agg_areas_df) %in%
    >    >   as.character(nuts_ll$FID))),] # dropping "NA"      "no_data"
    >    >
    >    > This should be ready to merge with the NUTS3 boundaries, if needed.
    >    >
    >    > agg_areas_df1$FID <- row.names(agg_areas_df1)
    >    > nuts_corine <- merge(nuts_laea, agg_areas_df1, by="FID")
    >    >
    >
    >    And to write out as GPKG:
    >
    >    names(nuts_corine)[1] <- "FID_"
    >    writeOGR(nuts_corine, "nuts_corine.gpkg", layer="corine", driver="GPKG")
    >
    >    It seems that at least this driver treats "FID" as a reserved field name.
    >
    >    > For the vector parts you could use sf and the provisional rgrass7sf on
    >    > github, but that wouldn't yet let you construct a skeleton SpatialGrid to
    >    > define the GRASS location. Using GRASS for the heavy lifting (the raster is
    >    > 51000 by 35000), and avoiding vector for overlay, this doesn't need much
    >    > memory (GRASS handles rasters by row). The GRASS temporary location only
    >    > takes 130MB of disk space. You could go for the 100m raster resolution, but I
    >    > doubt that the outcome would vary much - anyone like to try?
    >    >
    >    > If the sub-polygons by NUTS and corine categories are actually needed, the
    >    > output of r.cross could be passed to r.to.vect:
    >    >
    >    > execGRASS("r.to.vect", input="cross_nuts3", output="cross_nuts3",
    >    >   type="area")
    >    >
    >    > but this is more demanding in memory terms.
    >
    > Hi Roger,
    >
    > thanks a lot again for helping me with this issue.
    >
    >
    > Unfortunately, I haven't managed to call GRASS within R, neither install 
    > sf. My guess is that those issues are because I'm using both newest 
    > versions OS X High Sierra and R 3.5.0 which are not stable yet.
    
    You do not need sf. You do need GRASS, and, yes, OSX causes a lot of 
    problems because it is no longer attentive to the needs of numerical 
    analysts (certification of installs mandated at cost to FOSS communities; 
    gaping empty root password; only interested in pay-for software; never 
    contributes to FOSS AFAIK). Apple does not contribute to R.

Ah, I got it!
    
    >
    >    Reading into R is not possible, object too large.
    >
    > Bearing in mind the previous issues plus this last comment, I decided to 
    > use a PC with another OS (Ubuntu) aiming at solving them and working 
    > with a bit more space (32 GB).
    
    Wrong comment. The vector corine object is impossible to handle anywhere, 
    and probably should never have been constructed. I really doubt that it is 
    more "accurate" than the 100m raster, and doubt that the areas sums by 
    NUTS3 region differ much between 250m and 100m.


    
    You need to go back to the way in which Corine was derived, and to your 
    actual needs (which you have not described). If what you need are areas of 
    Corine classes by NUTS3 region, the code I provided gives you this. If 
    what you need is the full intersection of Corine classes and all NUTS3 
    regions, then you cannot visualize them (without zooming - rendering is 
    raster anyway) nor can you analyze them in any meaningful way, so you'd 
    need to revisit you research question. An intersection of a subset of 
    NUTS3 regions yielding raster patches or vector entities is possible and 
    could be visualized, but you seem to want the full extent of the NUTS3 
    regions.

My ultimate goal is to compute population within a buffer by downscaling the NUTS3 population on the CLC resolution using algorithms like in Gallego (2010): A population density grid of the European Union. One of them is based on a regression model so , yes, I need to compute the areas of CLC classes within each NUTS3 region. Thanks a lot again for the code. Regarding visualization, I'm planning to convey results at NUTS3 level.
    
    If you need the intersection between one/few NUTS3 region(s) and Corine, 
    you can still use the raster approach, but I don't know PostGIS well 
    enough to advise (forthcoming R Journal article; 
    https://cran.r-project.org/package=rpostgis). You can read the NUTS3 
    boundaries into R, but probably neither of the Corine vector files (not 
    just memory, you mentioned earlier that they suffered from topological 
    issues which would prevent intersection without intensive cleaning.

At some point I might need to implement it on a lower level - within a country for instance - so I will keep it on the lookout. I also will have a look on PostGIS.
    
    Using GRASS, you get the best of both worlds, script in R and run the 
    analysis at scale in GRASS using memory-conserving implementations.

Hot tip!

Roman.
    
    Roger
    
    >
    >    Roger
    >
    > In the meantime, I really would appreciate you guidance for gaining 
    > background on this subject. Could you please suggest me resources to 
    > better understand the features of objects involved in Spatial 
    > Statistics? I should mention that the knowledge I have about it is 
    > resumed in your book Applied Spatial Data Analysis with R.
    >
    >
    > Best,
    > Roman.
    >
    >    >
    >    > Interesting case, and it does show that combining GIS and R delivers the
    >    > goods - SAGA would probably work equivalently.
    >    >
    >    > Roger
    >    >
    >    >>
    >    >>  Roger
    >    >>
    >    >>>
    >    >>>   I really appreciate any feedback in advance as well as details that I
    >    >>>   should take into account to understand more about how to work with this
    >    >>>   kind of data. I will also keep you up to date on how it goes if you
    >    >>>   like.
    >    >>>
    >    >>>
    >    >>>   Best,
    >    >>>   Roman.
    >    >>>
    >    >>>   On 03/05/2018, 12:26, "Roger Bivand" <Roger.Bivand at nhh.no> wrote:
    >    >>>
    >    >>>      On Thu, 3 May 2018, Aguirre Perez, Roman wrote:
    >    >>>
    >    >>>    >   Hello Shaun,
    >    >>>    >
    >    >>>    >   Thanks a lot for replying and providing me alternative options.
    >    >>>    >
    >    >>>    >
    >    >>>    >   Unfortunately, I can't try both options anymore as I ran out of
    >    >>>    >   ArcGIS
    >    >>>    >   due to I was using a university PC which is not available now (I
    >    >>>    >   installed an ArcGIS trial version there), but I'll try it later. I
    >    >>>    >   also
    >    >>>    >   failed on installing the sf package - I'll dig a bit more on it.
    >    >>>    >   Nevertheless, I already downloaded the SpatialLite version so I'll
    >    >>>    >   try
    >    >>>    >   the second option and I'll let you know how it goes.
    >    >>>
    >    >>>      I think Melanie got it right - the apparent extra detail and
    >    >>>      precision
    >    >>>      you'd get from vector-vector overlay is illusory, so going with
    >    >>>      geoTiff
    >    >>>      should get you there (you can check to see whether 100m resolution
    >    >>>      differs
    >    >>>      from 250m). The only reason to choose vector-vector would be that the
    >    >>>      Corine vector contains categories not represented in the raster
    >    >>>      version.
    >    >>>      Using raster also steps around the polygon deficiencies in the GDB
    >    >>>      (and
    >    >>>      probably SQLite) representations.
    >    >>>
    >    >>>      Roger
    >    >>>
    >    >>>    >
    >    >>>    >
    >    >>>    >   Regards,
    >    >>>    >   Roman.
    >    >>>    >
    >    >>>    >   On 02/05/2018, 18:53, "Shaun Walbridge" <SWalbridge at esri.com>
    >    >>>    >   wrote:
    >    >>>    >
    >    >>>    >      Hello Roman,
    >    >>>    >
    >    >>>    >      A couple of suggested options: You can try and use the
    >    >>>    >      arcgisbinding package [1] to pull the data directly into R via
    >    >>>    >      ArcGIS, as you mentioned you have ArcGIS available [presumably
    >    >>>    >      on
    >    >>>    >      Windows or in a VM]. It will access the data directly, and let
    >    >>>    >      you
    >    >>>    >      create sp and sf objects out of Geodatabases with little work. A
    >    >>>    >      basic workflow looks like this:
    >    >>>    >
    >    >>>    >      d <- arc.open("path/file.gdb/layer_name")
    >    >>>    >      df <- arc.select(d) # here, you can filter columns and
    >    >>>    >      attributes,
    >    >>>    >      see [2]
    >    >>>    >      # create an sf object
    >    >>>    >      df.sf <- arc.data2sf(df)
    >    >>>    >      # alternatively, create an sp object
    >    >>>    >      df.sp <- arc.data2sp(df)
    >    >>>    >
    >    >>>    >      You can also write the results back to a geodatabase, or any
    >    >>>    >      other
    >    >>>    >      format that ArcGIS understands. Another option is trying the
    >    >>>    >      SpatiaLite version of the data at the URL you posted. You should
    >    >>>    >      be able to access this using R directly, provided your rgdal
    >    >>>    >      installation is correctly built to read spatialite databases. If
    >    >>>    >      it is, try the same process you mentioned using rgdal, but point
    >    >>>    >      it at the SpatialLite database instead. You could also use
    >    >>>    >      command-line OGR to convert the data, that has a few options
    >    >>>    >      like
    >    >>>    >      where clause filtering that aren't directly available via
    >    >>>    >      readOGR.
    >    >>>    >
    >    >>>    >      If neither of these options work, let me know and I can convert
    >    >>>    >      the data for you into a format of your preference.
    >    >>>    >
    >    >>>    >      Cheers,
    >    >>>    >      Shaun
    >    >>>    >
    >    >>>    >      1.
    >    >>>    >      https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_R-2DArcGIS_r-2Dbridge-2Dinstall&d=DwIGaQ&c=n6-cguzQvX_tUIrZOS_4Og&r=yckcjR6k3nADiVsNiAhGwcZB--0A8DQgvLSJ27upmyk&m=dkecE8PWOn5sSrtSXqX2R-VwJuFH_In4BvpC5da4LJ0&s=nRO2IG9dlrdKYGMSp3rCf7nwJqRFQoIWnY5zSFrPOQM&e=
    >    >>>    >      2.
    >    >>>    >      https://urldefense.proofpoint.com/v2/url?u=https-3A__rdrr.io_github_R-2DArcGIS_r-2Dbridge_man_arc.select.html&d=DwIGaQ&c=n6-cguzQvX_tUIrZOS_4Og&r=yckcjR6k3nADiVsNiAhGwcZB--0A8DQgvLSJ27upmyk&m=dkecE8PWOn5sSrtSXqX2R-VwJuFH_In4BvpC5da4LJ0&s=89N-cLe5N3dhZ6MTsM2OAYwmDImBH88ZrVaA5Hos0n4&e=
    >    >>>    >
    >    >>>    >
    >    >>>    >
    >    >>>    >      On 5/2/18, 1:34 PM, "R-sig-Geo on behalf of Aguirre Perez,
    >    >>>    >      Roman"
    >    >>>    >      <r-sig-geo-bounces at r-project.org on behalf of
    >    >>>    >      ra454 at exeter.ac.uk>
    >    >>>    >      wrote:
    >    >>>    >
    >    >>>    >          Hi everyone,
    >    >>>    >
    >    >>>    >          I’ve been struggling with a ESRI Geodatabase file
    >    >>>    >          (clc12_Version_18_5.gdb) which is a layer of land cover
    >    >>>    >          classes available on
    >    >>>    >
    >    >>>    >          https://urldefense.proofpoint.com/v2/url?u=https-3A__land.copernicus.eu_pan-2Deuropean_corine-2Dland-2Dcover_clc-2D2012-3Ftab-3Ddownload&d=DwIGaQ&c=n6-cguzQvX_tUIrZOS_4Og&r=YFaRLkcUCdDkLrpTbNOUV9J1CwYBCTMwgm5tdQkRSm4&m=qIGI8rXMP_JTDhSFz8NjjQMAyNAnpnUGFRBxqfH4bPU&s=9LaO4HiB5C5ewiuN_IeSQJSgq2tl5_-oMECPChtZa_U&e=
    >    >>>    >
    >    >>>    >          whose size is 2.61 GB once unzipped.
    >    >>>    >
    >    >>>    >          My ultimate task is to overlay it with the last NUTS3
    >    >>>    >          administrative boundaries shapefile (2013) available on
    >    >>>    >
    >    >>>    >          https://urldefense.proofpoint.com/v2/url?u=http-3A__ec.europa.eu_eurostat_web_gisco_geodata_reference-2Ddata_administrative-2Dunits-2Dstatistical-2Dunits&d=DwIGaQ&c=n6-cguzQvX_tUIrZOS_4Og&r=YFaRLkcUCdDkLrpTbNOUV9J1CwYBCTMwgm5tdQkRSm4&m=qIGI8rXMP_JTDhSFz8NjjQMAyNAnpnUGFRBxqfH4bPU&s=VExYSoR8FY_vhZaPNJpoOx0ZCZNMU9hMTtlGJZj2joU&e=
    >    >>>    >
    >    >>>    >          in order to compute the area covered by each class within
    >    >>>    >          each
    >    >>>    >          NUTS3 region.
    >    >>>    >
    >    >>>    >          Despite the ease of friendly software for performing this
    >    >>>    >          task, haven’t been capable of doing it - GRASS didn’t load
    >    >>>    >          the
    >    >>>    >          file as the log reports problems with the polygons, QGIS
    >    >>>    >          shows
    >    >>>    >          a warning regarding a specific object and ArcGIS got frozen.
    >    >>>    >          I
    >    >>>    >          guess it’s because the PC I used doesn’t have enough
    >    >>>    >          capacity.
    >    >>>    >          Unfortunately, I don’t have access to a more powerful one.
    >    >>>    >
    >    >>>    >          Anyway, I decided to try with R -after all, I’ll perform my
    >    >>>    >          analysis with it. So I started exploring this GDB with
    >    >>>    >          rgdal:
    >    >>>    >
    >    >>>    >          ogrInfo(dsn="clc12_Version_18_5.gdb",layer="clc12_Version_18_5")
    >    >>>    >
    >    >>>    >          Source:
    >    >>>    >          "/Users/Roman/Desktop/clc12gdb/clc12_Version_18_5.gdb",
    >    >>>    >          layer: "clc12_Version_18_5"
    >    >>>    >          Driver: OpenFileGDB;
    >    >>>    >          number of rows: 2370829
    >    >>>    >          Feature type: wkbPolygon with 3 dimensions
    >    >>>    >          Extent: (-2693292 -3086662) - (10037210 5440568)
    >    >>>    >          Null geometry IDs: 2156240
    >    >>>    >          CRS: +proj=laea +lat_0=52 +lon_0=10 +x_0=4321000
    >    >>>    >          +y_0=3210000
    >    >>>    >          +ellps=GRS80 +units=m +no_defs
    >    >>>    >          Number of fields: 6
    >    >>>    >          name                      type  length  typeName
    >    >>>    >          1 code_12              4       3           String
    >    >>>    >          2 ID                         4       18         String
    >    >>>    >          3 Remark               4       20         String
    >    >>>    >          4 Area_Ha             2       0           Real
    >    >>>    >          5 Shape_Length   2       0           Real
    >    >>>    >          6 Shape_Area       2       0           Real
    >    >>>    >
    >    >>>    >          Then I tried to load it typing
    >    >>>    >
    >    >>>    >          clc<-readOGR(dsn="clc12_Version_18_5.gdb",layer="clc12_Version_18_5")
    >    >>>    >
    >    >>>    >          After 3-5 minutes, it appears the following text:
    >    >>>    >
    >    >>>    >          OGR data source with driver: OpenFileGDB
    >    >>>    >          Source:
    >    >>>    >          "/Users/Roman/Desktop/clc12shp/clc12_Version_18_5.gdb",
    >    >>>    >          layer:
    >    >>>    >          "clc12_Version_18_5"
    >    >>>    >          with 2370829 features
    >    >>>    >          It has 6 fields
    >    >>>    >
    >    >>>    >          Unfortunately, after trying 5 times (each one took around 8
    >    >>>    >          hours) I couldn’t get anything but the following messages:
    >    >>>    >
    >    >>>    >          Warning messages:
    >    >>>    >          1: In readOGR(dsn = "clc12_Version_18_5.gdb", layer =
    >    >>>    >          "clc12_Version_18_5") :
    >    >>>    >          Dropping null geometries: 2156240
    >    >>>    >          2: In readOGR(dsn = "clc12_Version_18_5.gdb", layer =
    >    >>>    >          "clc12_Version_18_5") :
    >    >>>    >          Z-dimension discarded
    >    >>>    >
    >    >>>    >          Could anyone advise me how to tackle it? I also would
    >    >>>    >          appreciate suggestions on how to work with geodatabases -
    >    >>>    >          it’s
    >    >>>    >          my first time I work with these kind of files so I don’t
    >    >>>    >          even
    >    >>>    >          know their structure.
    >    >>>    >
    >    >>>    >          By the way, these are my computer and software
    >    >>>    >          specifications:
    >    >>>    >
    >    >>>    >          MacBook Pro 2012
    >    >>>    >          Processor 2.6 GHz Intel Core i7
    >    >>>    >          Memory 16 GB DDR3
    >    >>>    >          R 3.5.0
    >    >>>    >          RStudio 1.1.447
    >    >>>    >
    >    >>>    >
    >    >>>    >          Best,
    >    >>>    >          Roman.
    >    >>>    >
    >    >>>    >
    >    >>>    >
    >    >>>    >
    >    >>>    >   _______________________________________________
    >    >>>    >   R-sig-Geo mailing list
    >    >>>    >   R-sig-Geo at r-project.org
    >    >>>    >   https://stat.ethz.ch/mailman/listinfo/r-sig-geo
    >    >>>
    >    >>>      --
    >    >>>      Roger Bivand
    >    >>>      Department of Economics, Norwegian School of Economics,
    >    >>>      Helleveien 30, N-5045 Bergen, Norway.
    >    >>>      voice: +47 55 95 93 55; e-mail: Roger.Bivand at nhh.no
    >    >>>      http://orcid.org/0000-0003-2392-6140
    >    >>>      https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en
    >    >>>
    >    >>>
    >    >>
    >    >>
    >    >
    >    >
    >
    >    --
    >    Roger Bivand
    >    Department of Economics, Norwegian School of Economics,
    >    Helleveien 30, N-5045 Bergen, Norway.
    >    voice: +47 55 95 93 55; e-mail: Roger.Bivand at nhh.no
    >    http://orcid.org/0000-0003-2392-6140
    >    https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en
    >
    >
    
    -- 
    Roger Bivand
    Department of Economics, Norwegian School of Economics,
    Helleveien 30, N-5045 Bergen, Norway.
    voice: +47 55 95 93 55; e-mail: Roger.Bivand at nhh.no
    http://orcid.org/0000-0003-2392-6140
    https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en



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