2. mapview advanced controls

Source: vignettes/articles/mapview_02-advanced.Rmd

Despite the possibility to quickly plot spatial data, mapview has a set of arguments for finer control of the visualization. Depending on the object class, these are:

All types

  • map - the leaflet or mapview map to use -> default NULL
  • col.regions - the color palette for colouring raster, polygon and point areas (points are essentially circles) -> default hcl.colors with palette "Inferno" for raster data and palette "viridis" for vector data
  • at - breakpoints used for the colouring -> default NULL meaning they are calculated automatically for the range of data
  • na.color - the color for NA values -> default #BEBEBE80
  • map.types - the types of the background maps -> default CartoDB.Positron, CartoDB.DarkMatter, OpenStreetMap, Esri.WorldImagery, OpenTopoMap see here for available map types
  • alpha.regions - the opacity of raster, polygon and point fills -> default 0.8 for raster, 0.6 for polygons and 0.9 for points
  • legend - whether to add a legend to the plot -> default FALSE
  • legend.opacity - opacity of the legend -> default 1
  • verbose - whether to print additional information to the console during the rendering -> default FALSE
  • layer.name - the layer name to be used for plotting -> default depends on call. For a single object the name of the object; if zcol is supplied a combination of object name and column name; for raster stack/bricks the layer names
  • … - further arguments to be passed on to respective leaflet functions such as addRasterImage or adCircleMarkers

raster only

  • maxpixels - the maximum number of pixels to plot -> default 500k. This is used so rendering doesn’t take forever. This can also be set with mapviewOptions()
  • use.layer.names - whether to use the layer names of raster objects -> default FALSE
  • trim - should rasters be trimmed off NA values around the edges -> default TRUE

vector only

  • zcol - attribute name(s) or column number(s) in attribute table of the column(s) to be rendered -> default NULL
  • burst - whether to show all (TRUE) or only one (FALSE) layer(s) -> default FALSE
  • color - color (palette) for lines -> default hcl.colors(n, palette = "viridis")
  • alpha - opacity of the lines -> default 0.9
  • cex - circle size for point data -> default 6. This can also be used to map circle size to an attribute from the object’s attribute table by supplying either column name or number
  • lwd - line width -> default 2 for lines and points, 1 for polygons
  • label - a character vector of labels to be shown on mouseover -> default feature IDs, if zcol is set the values of zcol
  • popup - the popup function to use for the popups -> default popupTable(). See chapter on popups for further options

Here’s a few examples of how selected arguments can be used:

Adjusting color, col.regions & at

Similar to the good old spplot, arguments col.regions and at can be used for finer control of the colouring

library(mapview)
library(raster)

pal = mapviewPalette("mapviewTopoColors")

kili_data <- system.file("extdata", "kiliNDVI.tif", package = "mapview")
kiliNDVI <- stack(kili_data)
## Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj
## = prefer_proj): Discarded datum Unknown based on Clarke 1880 mod. ellipsoid in
## Proj4 definition
mapview(kiliNDVI[[1]], col.regions = pal(100), at = seq(-0.2, 1, 0.2), legend = TRUE)
## Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj =
## prefer_proj): Discarded ellps WGS 84 in Proj4 definition: +proj=merc +a=6378137
## +b=6378137 +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +k=1 +units=m +nadgrids=@null
## +wktext +no_defs +type=crs
## Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj =
## prefer_proj): Discarded datum World Geodetic System 1984 in Proj4 definition
## Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj =
## prefer_proj): Discarded ellps WGS 84 in Proj4 definition: +proj=merc +a=6378137
## +b=6378137 +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +k=1 +units=m +nadgrids=@null
## +wktext +no_defs +type=crs
## Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj =
## prefer_proj): Discarded datum World Geodetic System 1984 in Proj4 definition


mapview(breweries, zcol = "founded", at = seq(1400, 2200, 200), legend = TRUE)

Changing map.types

To use a different background map, use argument map.types

mapview(breweries, map.types = c("Esri.WorldShadedRelief", "OpenStreetMap.DE"), color = "grey40")

Individual layer.name(s)

To individually label the layer names use argument layer.name

mapview(list(franconia, breweries),
        layer.name = c("Franconian districts", "Franconian breweries"))

Using burst

burst can be used to plot all layers of an object

mapview(breweries, burst = TRUE)