shaperead
Read vector features and attributes from shapefile
Description
reads the shapefile specified by S
= shaperead(filename
)filename
and returns a
geographic data structure array in projected map coordinates (a mapstruct). The
geographic data structure combines geometric and feature attribute information.
shaperead
supports the ordinary 2-D shape types:
'Point'
, 'Multipoint'
,
'PolyLine'
, and 'Polygon'
.
returns a subset of the shapefile contents in S
= shaperead(filename
,Name,Value
)S
, as determined
by the name-value pair arguments. Use RecordNumbers
,
BoundingBox
, and Selector
to select
which features to read. If you use more than one of these parameters in the same
call, you receive the intersection of the records that match the individual
specifications. For instance, if you specify values for both
RecordNumbers
and BoundingBox
, you import
only those features with record numbers that appear in your list and that also have
bounding boxes intersecting the specified bounding box.
If you do not specify any parameters, shaperead
returns an
entry for every non-null feature and creates a field for every attribute.
Examples
Read Entire Shapefile
Read the entire shapefile called concord_hydro_line.shp
, including the attributes in concord_hydro_line.dbf
. The shaperead
function returns a mapstruct
with x and y coordinate vectors.
S = shaperead('concord_hydro_line.shp')
S=237×1 struct array with fields:
Geometry
BoundingBox
X
Y
LENGTH
Read Portion of Shapefile Based on Bounding Box
Specify a bounding box to limit the data returned by shaperead
. In addition, specify the names of the attributes you want to read.
bbox = [2.08 9.11; 2.09 9.12] * 1e5; S = shaperead('concord_roads.shp','BoundingBox',bbox,... 'Attributes',{'STREETNAME','CLASS'})
S=87×1 struct array with fields:
Geometry
BoundingBox
X
Y
STREETNAME
CLASS
Read road data by class from shapefile
Read road data only for class 4 and higher road segments that are at least 200 meters in length. Note the use of an anonymous function in the selector.
S = shaperead('concord_roads.shp','Selector',... {@(v1,v2) (v1 >= 4) && (v2 >= 200),'CLASS','LENGTH'})
S=115×1 struct array with fields:
Geometry
BoundingBox
X
Y
STREETNAME
RT_NUMBER
CLASS
ADMIN_TYPE
LENGTH
Determine the number of roads of each class.
n = histcounts([S.CLASS],'BinLimits',[1 7],'BinMethod','integer')
n = 1×7
0 0 0 7 93 15 0
Display a histogram of the number of roads that fall in each category of length.
figure histogram([S.LENGTH])
Read Shapefile with Geographic Coordinates
Specify that a shapefile uses latitude and longitude coordinates using the 'UseGeoCoords'
name-value pair.
For instance, return information about a shapefile as a structure. Verify the shapefile uses latitude and longitude coordinates by querying the CoordinateReferenceSystem
field. The shapefile uses latitude and longitude coordinates if the field contains a geocrs
object.
info = shapeinfo('landareas.shp');
crs = info.CoordinateReferenceSystem
crs = geocrs with properties: Name: "WGS 84" Datum: "World Geodetic System 1984" Spheroid: [1x1 referenceEllipsoid] PrimeMeridian: 0 AngleUnit: "degree"
Read the shapefile by using the shaperead
function. Indicate that the shapefile uses latitude and longitude coordinates using the 'UseGeoCoords'
name-value pair.
S = shaperead('landareas.shp','UseGeoCoords',true)
S=537×1 struct array with fields:
Geometry
BoundingBox
Lon
Lat
Name
Note that the shaperead
function returns a geographic data structure with latitude and longitude fields (a geostruct
).
Input Arguments
filename
— File name
character vector | string scalar
File name, specified as a string scalar or character vector.
filename
refers to the base name or full name of
one of the component files in a shapefile. If the main file (with extension
.shp
) is missing, shaperead
throws
an error. If either of the other files is missing,
shaperead
issues a warning.
Make sure that your machine is set to the same character encoding scheme
as the data you are importing. For example, if you are trying to import a
shapefile that contains Japanese characters, configure your machine to
support the Shift-JIS
encoding scheme.
Name-Value Arguments
Specify optional pairs of arguments as
Name1=Value1,...,NameN=ValueN
, where Name
is
the argument name and Value
is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.
Before R2021a, use commas to separate each name and value, and enclose
Name
in quotes.
Example: 'Attributes',{'STREETNAME','LENGTH'}
RecordNumbers
— Record numbers
vector of integers
Record numbers, specified as the comma-separated pair consisting of
'RecordNumbers'
and a vector of integers. Use the
parameter RecordNumbers
to import only features with
listed record numbers.
Data Types: double
BoundingBox
— Bounding box
2-by-2 matrix
Bounding box, specified as the comma-separated pair consisting of
'BoundingBox'
and a 2-by-2 matrix.
BoundingBox
has the form
[xmin,ymin;xmax,ymax]
, for map coordinates, or
[lonmin,latmin;lonmax,latmax]
for geographic
coordinates. Use the parameter BoundingBox
to import
only features whose bounding boxes intersect the specified box. The
shaperead
function does not trim features that
partially intersect the box.
Data Types: double
Selector
— Selector
cell array
Selector, specified as the comma-separated pair consisting of
'Selector'
and a cell array containing a function
handle and one or more attribute names. The function must return a
logical
scalar. Use the
Selector
parameter to import only features for
which the function, when applied to the corresponding attribute values,
returns true
. For more information about function
handles, see Create Function Handle.
Attributes
— Attribute names
cell array
Attribute names, specified as the comma-separated pair consisting of
'Attributes'
and a cell array of attribute names.
Use the parameter Attributes
to include listed
attributes and set the order of attributes in the structure array. Use
{}
to omit all attributes.
UseGeoCoords
— Flag to return shapefile contents in a geostruct
false
(default) | true
Flag to return shapefile contents in a geostruct, specified as the
comma-separated pair consisting of 'UseGeoCoords'
and
false
or true
.
When UseGeoCoords
is set to
true
, the shapefile contents are returned in a
geostruct. Use this parameter when you know that the
x- and y- coordinates in
the shapefile actually represent longitude and latitude data.
To determine whether a shapefile uses latitude and longitude data,
first use the shapeinfo
function to
return information about the shapefile as a structure. Then query the
CoordinateReferenceSystem
field of the structure.
The shapefile uses geographic coordinates if
CoordinateReferenceSystem
is a geocrs
object.
This code shows how to query the
CoordinateReferenceSystem
field of a structure
associated with the shapefile
landareas.shp
.
info = shapeinfo('landareas.shp');
info.CoordinateReferenceSystem
Output Arguments
S
— Vector geographic features
geographic data structure array
Vector geographic features, returned as an N-by-1 geographic data structure array containing one element for each non-null, spatial feature in the shapefile. The structure array has these fields:
Field | Description |
---|---|
Geometry | Type of shape, returned as
Individual points, lines, and polygons can have multiple parts. For example, lines can contain disconnected line segments, and polygons can have rings. All parts of an individual shape share the attributes specified for that shape by the corresponding attribute fields. When you read PolyLine shapes,
the This function does not support 3-D or measured shape types (PointZ, PointM, MultipointZ, MultipointM, PolyLineZ, PolyLineM, PolygonZ, PolylineM, and Multipatch). The function also ignores null point shapes. |
BoundingBox | Minimum and maximum coordinate values for the
shape, returned as a 2-by-2 numeric matrix of the
form |
X | x-coordinates, returned as a
row vector of data type |
Y |
y-coordinates, returned as a row
vector of data type |
Lon | Longitude coordinates, returned as a row
vector of data type |
Lat | Latitude coordinates, returned as a row vector
of data type |
Attribute fields | Attribute fields, returned as character vectors or numeric scalars. The
|
By default, the shaperead
function assumes that the
shapefile contains map coordinates and reads the data into a mapstruct
array. When your shapefile contains geographic coordinates, you can read the
data into a geostruct array by specifying the
UseGeoCoords
name-value argument as
true
.
For more information about geographic data structures, mapstruct arrays, and geostruct arrays, see Geographic Data Structures.
A
— Feature attribute information
N-by-1 attribute structure array
Feature attribute information, returned as an N-by-1
attribute structure array corresponding to array
S
.
The fields in the output structure arrays S
and
A
depend on the type of shape contained in the file and the names
and types of attributes included in the file. The shaperead
function
supports the following four attribute types: numeric
and
floating
(stored as type double
in MATLAB®) and character
and date
(stored as
char array
).
More About
Shapefile format
Data files in the shapefile format store vector data using multiple files: a main
file (.shp
), an index file (.shx
), and an
attribute file (.dbf
). All the files have the same base name, for
example, myfile.shp
, myfile.shx
, and
myfile.dbf
.
Tips
To get information about the coordinate reference system (CRS) associated with a
shapefile, use the shapeinfo
function.
Version History
Introduced before R2006a
Comando de MATLAB
Ha hecho clic en un enlace que corresponde a este comando de MATLAB:
Ejecute el comando introduciéndolo en la ventana de comandos de MATLAB. Los navegadores web no admiten comandos de MATLAB.
Select a Web Site
Choose a web site to get translated content where available and see local events and offers. Based on your location, we recommend that you select: .
You can also select a web site from the following list:
How to Get Best Site Performance
Select the China site (in Chinese or English) for best site performance. Other MathWorks country sites are not optimized for visits from your location.
Americas
- América Latina (Español)
- Canada (English)
- United States (English)
Europe
- Belgium (English)
- Denmark (English)
- Deutschland (Deutsch)
- España (Español)
- Finland (English)
- France (Français)
- Ireland (English)
- Italia (Italiano)
- Luxembourg (English)
- Netherlands (English)
- Norway (English)
- Österreich (Deutsch)
- Portugal (English)
- Sweden (English)
- Switzerland
- United Kingdom (English)