filterm

Filter latitudes and longitudes based on underlying data grid

Syntax

[latout,lonout] = filterm(lat,lon,Z,R,allowed)

[latout,lonout,indx] = filterm(___)

Description

[latout,lonout] = filterm(lat,lon,Z,R,allowed) filters a set of latitudes and longitudes to include only those data points which have a corresponding value in Z equal to allowed. R is a geographic raster reference object.

[latout,lonout,indx] = filterm(___) filters a set of latitudes and longitudes, returning indices of the included points in indx.

Examples

Filter Elevation Data

Display points along the equator that are above sea level.

First, load elevation raster data and a geographic cells reference object. The raster contains terrain heights relative to mean sea level. Then, specify the coordinates of evenly spaced points along the equator.

load topo60c
lon = (0:5:360)';
lat = zeros(size(lon));

Create a logical array representing the terrain above sea level. Then, filter the points along the equator to include only the elements that contain true.

topoASL = topo60c > 0; 
[newlat,newlon] = filterm(lat,lon,topoASL,topo60cR,1);

Create a world map and display the elevation data. Display the all of the points along the equator using red markers. Then, display the points that are above sea level using yellow circles.

worldmap world
geoshow(topo60c,topo60cR,'DisplayType','texturemap')
demcmap(topo60c)
geoshow(lat,lon,'DisplayType','point','MarkerEdgeColor','r')
geoshow(newlat,newlon,'DisplayType','point','Marker','o',...
    'MarkerFaceColor','y')

Input Arguments

lat — Latitude values

numeric array

Latitude values, specified as a numeric array.

Data Types: single | double

lon — Longitude values

numeric array

Longitude values, specified as a numeric array.

Data Types: single | double

Z — Filter

numeric array

Filter, specified as a numeric array.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical

R — Spatial referencing information

GeographicCellsReference object | GeographicPostingsReference object

Spatial referencing information, specified as a GeographicCellsReference object or a GeographicPostingsReference object. The RasterSize property of R must be consistent with size(Z).

Data Types: double

allowed — Allowed values

numeric array or character vector

Allowed values, specified as a numeric array or character vector.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char

Output Arguments

latout — Latitudes of filtered points

numeric array

Latitudes of filtered points, returned as a numeric array.

lonout — Longitudes of filtered points

numeric array

Longitudes of filtered points, returned as a numeric array.

indx — Indices of filtered points

numeric array

Indices of filtered points, returned as a numeric array.

Version History

Introduced before R2006a

R2024b: filterm does not accept referencing vectors or referencing matrices as input

The filterm function does not accept referencing vectors or referencing matrices as input. Use a geographic raster reference object, specified as a GeographicCellsReference or GeographicPostingsReference object, as input instead. Reference objects have several advantages over referencing vectors and referencing matrices.

• Unlike referencing vectors and referencing matrices, reference objects have properties that document the size of the associated raster, its geographic limits, and the direction of its rows and columns.

• You can manipulate the limits of geographic rasters associated with reference objects using the geocrop function.

• You can manipulate the size and resolution of geographic rasters associated with reference objects using the georesize function.

To update your code, create a geographic reference object.

• Create a geographic reference object for a raster of cells by using the georefcells function.

• Create a geographic reference object for a raster of regularly posted samples by using the georefpostings function.

• Convert from a referencing vector to a geographic reference object by using the refvecToGeoRasterReference function.

• Convert from a referencing matrix to a geographic reference object by using the refmatToGeoRasterReference function.

Once you have created a reference object, replace uses of the referencing vector or referencing matrix in your code with the reference object.

R2023b: filterm will not accept referencing vectors or referencing matrices as input

When you specify a referencing vector or referencing matrix as input, the filterm function issues a warning that it will not accept referencing vectors or referencing matrices as input in a future release.