modifying vertices of geopolyshape

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Murat Panayirci
Murat Panayirci 2022-11-8
移动：Walter Roberson 2025-8-16，4:32
Hi,
I can modify an existing polyshape plot as follows:
Vertices = [0 0 2 2; 2 0 0 2]';
NewVertices = [0 0 2 2; 2 0 0 3]';
pgon = polyshape(Vertices);
p = plot(pgon,'FaceColor','red','FaceAlpha',0.1);
p.Shape.Vertices = NewVertices;
however I can't do the same thing with geopolyshape, since I could not find any properties of it which stores the lat,lon coords. Essentially, I want to enable moving a geopolyshape incrementally with user commands. I would be glad if you anybody could advise.
Thank you,
Murat

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回答（2 个）

Geetla Sindhu
Geetla Sindhu 2022-11-11
Hello Murat,
I understand that you are trying to use geopolyshape with geographic coordinates.
You can try the following workaround to solve the issue:
  • A geopolyshape object represents a polygon or multipolygon in geographic coordinates. Use the geopolyshape function.
shape = geopolyshape(lat,lon)
This function creates a polygon with vertices at the specified latitude and longitude coordinates.
  • Then geoplot is used to plot the point, line, or polygon shape objects in shape on a geographic axes.
pg = geoplot(shape)
Now pg is a polygon object with different properties and they be accessed using dot notation.
For example:
shape = geopolyshape([1 10 1 1],[1 1 10 1] );
pg = geoplot(shape);
pg.FaceColor = "r";
Hope this resolves your issue.
You can also refer to Geographic polygon appearance and behavior - MATLAB (mathworks.com) for further information regarding polygon properties.
Thank you.
  1 个评论
Murat Panayirci
Murat Panayirci 2022-11-11
移动：Walter Roberson 2025-8-16，4:32
Hi Geetla,
my problem is that the object pg you created with geoplot does not have a "Vertices" field (as in the regular polyshape plot) which I can modify. see below
shape = geopolyshape([1 10 1 1],[1 1 10 1] );
pg = geoplot(shape);
>> pg.ShapeData
ans =
geopolyshape with properties:
NumRegions: 1
NumHoles: 0
Geometry: "polygon"
CoordinateSystemType: "geographic"
GeographicCRS: []
>> pgon = polyshape([0 0 2 2],[2 0 0 2]);
>> p = plot(pgon,'FaceColor','red','FaceAlpha',0.1);
>> p.Shape
ans =
polyshape with properties:
Vertices: [4×2 double]
NumRegions: 1
NumHoles: 0
as you can see pg.ShapeData or any other field that I checked does not enable me to easily update the geoplot by updating the coords of vertices. Whereas for polyshape, I can do that as I have mentioned in my original post.
So my question is: how can I modify the geoplot of a geopolyshape, without replotting it?
thanks,
Murat

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Kelly Kearney
Kelly Kearney 2025-8-16，0:11
编辑：Kelly Kearney 2025-8-16，0:11
Ran in:
Old question, but I was working through this same problem when needing to reproject a mappolyshape. It appears that the vertex coordinates are hidden in the undocumented object properties InternalData.VertexCoordinateData1 and InternalData.VertexCoordinateData2. They appear to be modifiable*.
shape = geopolyshape([1 10 1 1],[1 1 10 1]);
geoplot(shape);
hold on
shape.InternalData.VertexCoordinate2 = [1 1 5 1];
geoplot(shape, 'r')
*usual disclaimer that undocumented stuff is liable to change and thus break code. I tested this to R2023a and the Answers site used 2024b to render this.

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