# BGM examples

#### Michael D. Sumner

#### 2025-04-03

# Available BGM examples

The `bgmfiles` package contains several real-world example BGM files.

Obtain every available BGM file and plot in native coordinates.

    library(rbgm)
    library(bgmfiles)

    ## turn +proj into line separated text
    breakproj <- function(x) {
      paste(strsplit(x, " ")[[1]], collapse = "\n")
    }
    files <- bgmfiles()
    for (i in seq_along(files)) {
      bgm <- bgmfile(files[i])
      boxes <- boxSpatial(bgm)
      plot(boxes, col = ifelse(boxes$boundary, "#88888880", sample(rainbow(nrow(boxes), alpha = 0.5))))
      op <- par(xpd = NA)
      par(op)
      title(basename(files[i]), cex = 0.8)
      mtext(breakproj(proj4string(boxes)), cex = 0.75, side = 2, las = 1, adj = 0, line = 2, at = par("usr")[3], xpd = NA)

    }

    ## Warning in CPL_crs_from_input(x): GDAL Error 1: PROJ:
    ## proj_crs_get_coordinate_system: Object is not a SingleCRS

    ## OGR: Corrupt data

    ## Warning in CRS(crs, doCheckCRSArgs = FALSE): invalid PROJ4 string

    ## OGR: Corrupt data

    ## /usr/local/lib/R/site-library/bgmfiles/extdata/bgm/ams71.bgm
    ## file declares 187 faces but contains data for 193 faces
    ##
    ##  ... returning all 193 faces

Make one interactive map with all (code not run here to avoid dependencies).

    library(rbgm)
    library(bgmfiles)
    library(mapview)

    mp <- mapview()  ## empty map view

    fs <- bgmfiles::bgmfiles()  ## paths of all files collected
    cols <- rainbow(length(fs), alpha = 0.2)
    ## read in all boxes, convert to SpatialPolygonsDataFrame, and add to the map view
    for (i in seq_along(fs)) {
      mp <- mp + mapview(boxSpatial(bgmfile(fs[i])), color = cols[i], alpha = 0.3, layer.name = basename(fs[i]))
    }

    ## view the mapview
    mp