Use vector files for import and export of weights

Use vector files for import and export of weights, storing spatial entity coordinates in the arcs, and the entity indices in the data frame.

Usage

nb2lines(nb, wts, coords, proj4string=NULL, as_sf=FALSE)
listw2lines(listw, coords, proj4string=NULL, as_sf=FALSE)
df2sn(df, i="i", i_ID="i_ID", j="j", wt="wt")

Arguments

nb: a neighbour object of class nb
wts: list of general weights corresponding to neighbours
coords: matrix of region point coordinates, a Spatial object (points or polygons), or an sfc object (points or polygons)
proj4string: default NULL; if coords is a Spatial or sf object, this value will be used, otherwise the value will be converted appropriately
as_sf: output object in Spatial or sf format, default FALSE, set to TRUE if coords is an sfc object and FALSE if a Spatial object
listw: a listw object of spatial weights
df: a data frame read from a shapefile, derived from the output of nb2lines
i: character name of column in df with from entity index
i_ID: character name of column in df with from entity region ID
j: character name of column in df with to entity index
wt: character name of column in df with weights

Details

The neighbour and weights objects may be retrieved by converting the specified columns of the data slot of the SpatialLinesDataFrame object into a spatial.neighbour object, which is then converted into a weights list object.

Value

nb2lines and listw2lines return a SpatialLinesDataFrame object or an sf object; the data frame contains with the from and to indices of the neighbour links and their weights. df2sn converts the data retrieved from reading the data from df back into a spatial.neighbour object.

Author

Roger Bivand Roger.Bivand@nhh.no

Note

Original idea due to Gidske Leknes Andersen, Department of Biology, University of Bergen, Norway

Examples

columbus <- st_read(system.file("shapes/columbus.gpkg", package="spData")[1], quiet=TRUE)
col.gal.nb <- read.gal(system.file("weights/columbus.gal", package="spData")[1])
res <- listw2lines(nb2listw(col.gal.nb), st_geometry(columbus))
summary(res)
#>        i               j             i_ID               j_ID          
#>  Min.   : 1.00   Min.   : 1.00   Length:230         Length:230        
#>  1st Qu.:13.00   1st Qu.:13.00   Class :character   Class :character  
#>  Median :24.00   Median :24.00   Mode  :character   Mode  :character  
#>  Mean   :24.19   Mean   :24.19                                        
#>  3rd Qu.:35.00   3rd Qu.:35.00                                        
#>  Max.   :49.00   Max.   :49.00                                        
#>        wt               geometry  
#>  Min.   :0.1000   LINESTRING:230  
#>  1st Qu.:0.1429   epsg:NA   :  0  
#>  Median :0.1667                   
#>  Mean   :0.2130                   
#>  3rd Qu.:0.2500                   
#>  Max.   :0.5000                   
tf <- paste0(tempfile(), ".gpkg")
st_write(res, dsn=tf, driver="GPKG")
#> Writing layer `file3b434754c9c27d' to data source 
#>   `/tmp/Rtmp2GWLZN/file3b434754c9c27d.gpkg' using driver `GPKG'
#> Writing 230 features with 5 fields and geometry type Line String.
inMap <- st_read(tf)
#> Reading layer `file3b434754c9c27d' from data source 
#>   `/tmp/Rtmp2GWLZN/file3b434754c9c27d.gpkg' using driver `GPKG'
#> Simple feature collection with 230 features and 5 fields
#> Geometry type: LINESTRING
#> Dimension:     XY
#> Bounding box:  xmin: 6.165913 ymin: 11.04088 xmax: 10.96206 ymax: 14.43766
#> Projected CRS: Undefined Cartesian SRS with unknown unit
summary(inMap)
#>        i               j             i_ID               j_ID          
#>  Min.   : 1.00   Min.   : 1.00   Length:230         Length:230        
#>  1st Qu.:13.00   1st Qu.:13.00   Class :character   Class :character  
#>  Median :24.00   Median :24.00   Mode  :character   Mode  :character  
#>  Mean   :24.19   Mean   :24.19                                        
#>  3rd Qu.:35.00   3rd Qu.:35.00                                        
#>  Max.   :49.00   Max.   :49.00                                        
#>        wt                 geom    
#>  Min.   :0.1000   LINESTRING:230  
#>  1st Qu.:0.1429   epsg:NA   :  0  
#>  Median :0.1667                   
#>  Mean   :0.2130                   
#>  3rd Qu.:0.2500                   
#>  Max.   :0.5000                   
diffnb(sn2listw(df2sn(as.data.frame(inMap)))$neighbours, col.gal.nb)
#> Warning: style is M (missing); style should be set to a valid value
#> Warning: neighbour object has 49 sub-graphs
#> Neighbour list object:
#> Number of regions: 49 
#> Number of nonzero links: 0 
#> Percentage nonzero weights: 0 
#> Average number of links: 0 
#> 49 regions with no links:
#> 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
#> 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
#> 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49
#> 49 disjoint connected subgraphs
res1 <- listw2lines(nb2listw(col.gal.nb), as(columbus, "Spatial"))
summary(res1)
#> Object of class SpatialLinesDataFrame
#> Coordinates:
#>         min      max
#> x  6.221943 10.95359
#> y 11.010031 14.36908
#> Is projected: TRUE 
#> proj4string : [NA]
#> Data attributes:
#>        i               j             i_ID               j_ID          
#>  Min.   : 1.00   Min.   : 1.00   Length:230         Length:230        
#>  1st Qu.:13.00   1st Qu.:13.00   Class :character   Class :character  
#>  Median :24.00   Median :24.00   Mode  :character   Mode  :character  
#>  Mean   :24.19   Mean   :24.19                                        
#>  3rd Qu.:35.00   3rd Qu.:35.00                                        
#>  Max.   :49.00   Max.   :49.00                                        
#>        wt        
#>  Min.   :0.1000  
#>  1st Qu.:0.1429  
#>  Median :0.1667  
#>  Mean   :0.2130  
#>  3rd Qu.:0.2500  
#>  Max.   :0.5000