mapclip
Description
clips the specified planar point, line, or polygon shapes to the specified
xy-limits. Specify the shapes using clipped
= mapclip(shape
,xlimits
,ylimits
)shape
, the
x-limits using xlimits
, and the
y-limits using ylimits
.
To crop raster data that is represented by an array and a map raster reference object,
use the mapcrop
function
instead.
clips the shapes to the specified clipper polygon. (since R2024b)clipped
= mapclip(shape
,clipperPolygon
)
Examples
Clip Planar Shapes to xy-Limits
Read hydrography data as a geospatial table. Extract the polygon shape for a pond.
hydro = readgeotable("concord_hydro_area.shp");
shape = hydro.Shape(14)
shape = mappolyshape with properties: NumRegions: 1 NumHoles: 3 Geometry: "polygon" CoordinateSystemType: "planar" ProjectedCRS: [1×1 projcrs]
Specify the xy-limits and clip the shape.
xlimits = [207736 208212]; ylimits = [912283 912636]; clipped = mapclip(shape,xlimits,ylimits);
Display the shape and the clipped shape on a map.
figure
geoplot(shape)
hold on
geoplot(clipped)
Clip Planar Shape to Polygon
Since R2024b
Read road data for an area in Boston as a geospatial table. The table represents the roads using line shapes in planar coordinates. Extract the line shapes.
roads = readgeotable("boston_roads.shp");
shape = roads.Shape
shape=2795×1 maplineshape array with properties:
NumParts: [2795×1 double]
Geometry: "line"
CoordinateSystemType: "planar"
ProjectedCRS: [1×1 projcrs]
⋮
Specify the clipper polygon. Create a geospatial table that contains a point shape object for a named location in Boston. Then, define an area of interest (AOI) by creating a circle with a radius of 1000 meters that is centered on the point shape.
places = readgeotable("boston_placenames.shp"); flagstaff = geocode("FLAGSTAFF HILL",places); clipperPolygon = aoicircle(flagstaff,1000)
clipperPolygon = mappolyshape with properties: NumRegions: 1 NumHoles: 0 Geometry: "polygon" CoordinateSystemType: "planar" ProjectedCRS: [1×1 projcrs]
Verify that the road data and the AOI use the same projected coordinate reference system (CRS).
isequal(shape.ProjectedCRS,clipperPolygon.ProjectedCRS)
ans = logical
1
Clip the road data to the AOI.
clipped = mapclip(shape,clipperPolygon);
Create a map that displays the clipped road data, the named location, and the AOI.
figure geoplot(clipped,LineWidth=0.8) hold on geoplot(flagstaff,MarkerSize=20) geoplot(clipperPolygon,FaceColor="none")
Remove Shapes with No Coordinate Data from Output
Read the names and locations of places in Boston as a geospatial table. Extract the point shapes.
places = readgeotable("boston_placenames.shp");
shape = places.Shape
shape = 13x1 mappointshape array with properties: NumPoints: [13x1 double] X: [13x1 double] Y: [13x1 double] Geometry: "point" CoordinateSystemType: "planar" ProjectedCRS: [1x1 projcrs]
Specify the xy-limits and clip the shapes.
xlimits = [235226 237174]; ylimits = [900179 901059]; clipped = mapclip(shape,xlimits,ylimits);
When a point shape lies outside the specified limits, the clipped shape has no coordinate data and the NumPoints
property is 0
. Remove shapes with no coordinate data from the clipped shapes.
idx = clipped.NumPoints ~= 0; clipped = clipped(idx)
clipped = 5x1 mappointshape array with properties: NumPoints: [5x1 double] X: [5x1 double] Y: [5x1 double] Geometry: "point" CoordinateSystemType: "planar" ProjectedCRS: [1x1 projcrs]
When a line or polygon shape has no coordinate data, its respective the NumParts
or NumRegions
property is 0
.
Clip Projected Shape Using Geographic Limits
If your shape is in projected coordinates and your limits are in geographic coordinates, then you must project the geographic coordinates before clipping the shape. To use this approach:
You must know the projected coordinate reference system (CRS) for the shape. You can determine whether a shape object is associated with a projected CRS by querying the
ProjectedCRS
property.The projection method for the CRS must result in x-coordinates and y-coordinates that run approximately west-to-east and south-to-north, respectively, such as transverse Mercator or Lambert Conic Conformal. This approach is not valid for projection methods such as polar stereographic. You can find the projection method for a projected CRS object by querying the
ProjectionMethod
property.
Read road data for an area in Concord, MA as a geospatial table. Extract the line shapes.
roads = readgeotable("concord_roads.shp");
shape = roads.Shape
shape=609×1 object
16×1 maplineshape array with properties:
NumParts: [16×1 double]
Geometry: "line"
CoordinateSystemType: "planar"
ProjectedCRS: [1×1 projcrs]
⋮
Verify that the shape has a projected CRS with an appropriate projection method.
crs = shape.ProjectedCRS
crs = projcrs with properties: Name: "NAD83 / Massachusetts Mainland" GeographicCRS: [1×1 geocrs] ProjectionMethod: "Lambert Conic Conformal (2SP)" LengthUnit: "meter" ProjectionParameters: [1×1 map.crs.ProjectionParameters]
Specify the latitude and longitude limits using geographic coordinates. Project the latitude and longitude limits to xy-limits by using the projected CRS and the projfwd
function.
latlim = [42.4657 42.4687]; lonlim = [-71.3996 -71.3946]; [xlimits,ylimits] = projfwd(crs,latlim,lonlim);
Clip the shapes.
clipped = mapclip(shape,xlimits,ylimits);
Display the clipped shapes on a map. Compare the limits you specified with the limits of the plot by setting the tick format to decimal degrees.
figure
geoplot(clipped)
geotickformat("dd")
Input Arguments
shape
— Shape
mappointshape
, maplineshape
, or
mappolyshape
object | array of mappointshape
, maplineshape
, or
mappolyshape
objects
Shape, specified as a mappointshape
,
maplineshape
, or
mappolyshape
object or as an array of mappointshape
, maplineshape
,
or mappolyshape
objects. When you specify an array, you can include a
combination of point, line, and polygon shape objects.
xlimits
— x-limits
two-element vector
x-limits, specified as a two-element vector of the form
[xmin xmax]
, where xmax
is greater than
xmin
.
The units of xlimits
must match the units of
shape
. If the ProjectedCRS
property of
shape
contains a projcrs
object,
you can find the units by querying the LengthUnit
property of the
projcrs
object, for example
shape.ProjectedCRS.LengthUnit
.
ylimits
— y-limits
two-element vector
y-limits, specified as a two-element vector of the form
[ymin ymax]
, where ymax
is greater than
ymin
.
The units of ylimits
must match the units of
shape
. If the ProjectedCRS
property of
shape
contains a projcrs
object,
you can find the units by querying the LengthUnit
property of the
projcrs
object, for example
shape.ProjectedCRS.LengthUnit
.
clipperPolygon
— Clipper polygon
mappolyshape
object
Since R2024b
Clipper polygon, specified as a mappolyshape
object.
The ProjectedCRS
properties of
clipperPolygon
and shape
must be equal,
unless one of the ProjectedCRS
properties is empty.
Output Arguments
clipped
— Clipped shape
mappointshape
, maplineshape
, or
mappolyshape
object | array of mappointshape
, maplineshape
, or
mappolyshape
objects
Clipped shape, returned as a mappointshape
,
maplineshape
, or
mappolyshape
object or as an array of mappointshape
, maplineshape
,
or mappolyshape
objects.
clipped
has the same type and size as
shape
.
If an element of shape
lies completely outside the specified
limits, then the corresponding element of clipped
does not contain
coordinate data. When a point, line, or polygon shape does not contain coordinate data,
its respective NumPoints
, NumParts
, or
NumRegions
property is 0
.
Tips
If you clip a shape within a geospatial table, the function does not modify any attributes of the table.
Version History
Introduced in R2022aR2024b: Clip shape objects to polygon
Clip point, line, and polygon shape objects to a polygon shape.
See Also
Functions
Objects
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