R plot grid value on maps
geospatial, ggplot2, lattice, r
Solution
There are roughly two options: one using the lattice and sp package and the other using the ggplot2 package:
lattice / sp
First you have to transform your data to a `SpatialPixelsDataFrame` (provided by the sp-package), assuming your data is called `df`:
require(sp)
gridded(df) = c("lat","lon")
and then plotting:
spplot(df, "value")
overlaying additional information such as country boundaries can be done using the `sp.layout` argument:
spplot(df, "value", sp.layout = list("sp.lines", cntry_boundaries))
where `cntry_boundaries` is a `SpatialLines(DataFrame)`, or `SpatialPolygons(DataFrame)`. Reading a polygonset into R can be done using the `rgdal` package, or the `maptools` package (`readShapeLines`).
ggplot2
I personally prefer using `ggplot2` over `spplot`. `ggplot2` is more flexible and has a more clear syntax. Note that `ggplot2` works with normal `data.frame`'s, and not with the spatial objects of the sp-package.
A minimal example would look something like:
ggplot(aes(x = lat, y = lon), data = df) + geom_tile(aes(fill = value)) +
geom_path(data = cntry_boundaries)
For more information see these earlier answers of mine:
- Plotting interpolated data on map
- Average values of a point dataset to a grid dataset
Problem
I have several file with the following format: lat,lon,value. I would like to plot a colored grid map with such value for each one of the lat,lon point and overlapping it over the EU map. Thanks for support.