vec2mtx

Load a MAT file containing global coastline coordinates into the workspace. The variables within the MAT file, coastlat and coastlon, specify numeric latitude and longitude coordinates, respectively.

load coastlines

Convert the coordinates to a regular raster data grid and a geographic raster reference object. Specify 1 grid cell per degree of latitude and longitude. The vec2mtx function indicates that a grid cell corresponds to a coastline coordinate using 1 and uses 0 otherwise.

[Z,R] = vec2mtx(coastlat,coastlon,1);

Display the raster data on a map. Use black for the coastlines (Z == 1) and cyan for the other regions (Z == 0).

figure 
worldmap world
geoshow(Z,R,"DisplayType","texturemap")
colormap([0 1 1; 0 0 0])

Read a shapefile containing US state polygons into the workspace as a geospatial table. Extract the coordinates of the polygons by converting the geospatial table to a table.

states = readgeotable("usastatelo.shp");
T = geotable2table(states,["Latitude" "Longitude"]);
[lat,lon] = polyjoin(T.Latitude',T.Longitude');

Convert the coordinates to a regular raster data grid and a geographic raster reference object. Specify 5 grid cells per degree of latitude and longitude. When you specify the "filled" option, the vec2mtx function indicates that a grid cell is inside a polygon using 0, on a polygon boundary using 1, and outside all the polygons using 2.

[Z,R] = vec2mtx(lat,lon,5,"filled");

Display the raster data on a map. Use red for regions inside a polygon (Z == 0), white for regions on a boundary (Z == 1), and blue for regions outside all the polygons (Z == 2).

figure 
usamap(Z,R)
geoshow(Z,R,"DisplayType","texturemap")
colormap([1 0 0; 1 1 1; 0 0 1])

Read a shapefile containing US state polygons into the workspace as a geospatial table. Extract the coordinates of the state boundaries by converting the geospatial table to a table.

states = readgeotable("usastatelo.shp");
T = geotable2table(states,["Latitude" "Longitude"]);
[lat,lon] = polyjoin(T.Latitude',T.Longitude');

Create a reference object by using the georefcells function and specifying the geographic limits and extent of each cell (the inverse of the number of cells per degree). For this example, choose limits that include the conterminous US.

latlim = [22 52];
lonlim = [-130 -65];
cellsPerDegree = 5;
R = georefcells(latlim,lonlim,1/cellsPerDegree,1/cellsPerDegree);

Create a raster of zeros with a size that is consistent with R.

Z = zeros(R.RasterSize);

Overwrite Z and R with a new raster data grid that includes the state boundaries and interiors.

[Z,R] = vec2mtx(lat,lon,Z,R,"filled");

Plot the result on a map. Use red for the interior regions, white for the boundaries, and blue for the exterior regions.

figure
usamap(Z,R)
geoshow(Z,R,"DisplayType","texturemap")
colormap([1 0 0; 1 1 1; 0 0 1])

The vec2mtx function enables you to create raster data grids with two classification values (when lat and lon represent lines) or three classification values (when lat and lon represent polygons). To create a raster data grid with additional classification values, you can use vec2mtx multiple times and combine the output grids.

Read two files into the workspace:

load coastlines
rivers = readgeotable("worldrivers.shp");
T = geotable2table(rivers,["Latitude" "Longitude"]);
[latRiver,lonRiver] = polyjoin(T.Latitude',T.Longitude');

Convert the coastline coordinates to a regular raster data grid and a geographic raster reference object. Specify 1 cell per degree of latitude and longitude. When you specify the "filled" option, the vec2mtx function creates the grid using these rules:

[Z,R] = vec2mtx(coastlat,coastlon,1,"filled");

Convert the world river coordinates to a regular raster data grid and a geographic raster reference object. When you specify a raster data grid and a reference object as input, the vec2mtx function creates the new grid and reference object using the same latitude limits and number of cells per degree as the input reference object. The function creates the grid using these rules:

[riverZ,riverR] = vec2mtx(latRiver,lonRiver,Z,R);

Verify that the reference objects are the same.

isequal(R,riverR)

ans = logical
   1

Find the indices of the river grid that correspond to river coordinates. Then, replace those elements of the coastline grid with the value 3. As a result, each element of the coastline grid is one of four values (0, 1, 2, or 3).

idx = riverZ == 1;
Z(idx) = 3;

Display the grid on a map. Use green for the land areas, black for the coastlines, cyan for the ocean areas, and blue for the rivers.

figure
worldmap world
geoshow(Z,R,"DisplayType","texturemap")

landColor = [0.45 0.60 0.30];
coastColor = [0 0 0];
oceanColor = [0 1 1];
riverColor = [0 0 1];
colormap([landColor; coastColor; oceanColor; riverColor])