extractm
Coordinate data from line or patch display structure
extractm will be removed in a future release. The use of display
structures is not recommended. Use geoshape vectors instead.
Syntax
[lat,lon] = extractm(display_struct,object_str)
[lat,lon] = extractm(display_struct,object_strings)
[lat,lon] = extractm(display_struct,object_strings,searchmethod)
[lat,lon] = extractm(display_struct)
[lat,lon,indx] = extractm(...)
mat = extractm(...)
Description
[lat,lon] = extractm(display_struct,object_str)
extracts latitude and longitude coordinates from those elements of
display_struct having 'tag' fields that begin with
the string scalar or character vector specified by object_str.
display_struct is a Mapping Toolbox™ display structure in which the 'type' field has a value of
either 'line' or 'patch'. The output
lat and lon vectors include
NaNs to separate the individual map features. The comparison of
'tag' values is not case-sensitive.
[lat,lon] = extractm(display_struct,object_strings)
selects features with 'tag' fields matching any of several different
string scalar or character vectors. object_strings is a string scalar,
character vector, cell array of character vectors, or character array.
extractm strips trailing spaces from features listed in character
arrays before matching.
[lat,lon] = extractm(display_struct,object_strings,searchmethod)
specifies the method used to match the values of the 'tag' field in
display_struct. searchmethod can be one of these
values:
'strmatch' | Search for matches at the beginning of the tag |
'findstr' | Search within the tag |
'exact' | Search for exact matches. Note that when
searchmethod is specified the search is
case-sensitive. |
[lat,lon] = extractm(display_struct) extracts
all vector data from the input map structure.
[lat,lon,indx] = extractm(...) also returns the
vector indx identifying which elements of
display_struct met the selection criteria.
mat = extractm(...) returns the vector data in a single matrix,
where mat = [lat lon].
Examples
Extract the District of Columbia from the low-resolution U.S. vector data:
load greatlakes [lat, lon] = extractm(greatlakes, 'Erie'); axesm mercator geoshow(lat,lon, 'DisplayType','polygon', 'FaceColor','blue')
Tips
A Version 1 display structure is a MATLAB® structure that can contain line, patch, text, regular data grid, geolocated
data grid, and certain other objects and fixed attributes. In Mapping Toolbox Version 2, a new data structure for vector geodata was introduced (called a
mapstruct or a geostruct, depending on
whether coordinates it contains are projected or unprojected). Geostructs and mapstructs
have few required fields and can include any number of user-defined fields, giving them
much greater flexibility to represent vector geodata. For information about the contents
and format of display structures, see Version 1 Display Structures in the reference page for displaym. For information about converting display structures to geographic
data structures, see the reference page for updategeostruct, which performs such conversions.