Extract coordinates from a geopolyshape

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Given a geographic shape object of type geopolyshape:
us_states = readgeotable("usastatehi.shp")
montana = us_states.Shape(us_states.Name == "Montana")
class(montana)
ans =
'geopolyshape'
How could I extract a list of Lat/Lon coordinates of the given shape object (mo_lat, mo_lon)?
% montana
mo_lat = ??? % list of latitudes of Montana polygon edges
mo_lon = ??? % list of longitudes of Montana polygon edges
I know it's possible when loading data using shaperead function instead:
us_states = shaperead("usastatehi.shp")
montana = us_states(26); % 26 is Montana
mo_lat = montana.Y; % list of latitudes of Montana edges
mo_lon = montana.X; % list of longitudes of Montana edges
But I'm curious if it's possible to extract data from existing geopolyshape?

Accepted Answer

Jacob Halbrooks
Jacob Halbrooks on 8 Nov 2022
You can access latitude-longitude coordinates from a geopolyshape using the geotable2table function. We recognize that there is a need to make coordinate data access easier, but in the meantime you can use this approach as a workaround. For example, assuming your table contains geopolyshape data:
GT = readgeotable("myfile.shp");
T = geotable2table(GT,["Lat","Lon"]);
You can also extract the data into NaN-delimited arrays using polyjoin:
[lat,lon] = polyjoin(T.Lat,T.Lon);
  1 Comment
Sergey Kostrukov
Sergey Kostrukov on 11 Nov 2022
Thanks, loooks like this is a workaround. The optimal solution for now is to use shaperead I think.

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More Answers (2)

KSSV
KSSV on 12 Oct 2022
Edited: KSSV on 12 Oct 2022
The present version is much easier. Note that the class of us_states is a table. You can extract the column using:
us_states = readgeotable("usastatehi.shp") ;
class(us_states)
ans = 'table'
us_states.(1) % first column
ans =
16×1 geopolyshape array with properties: NumRegions: [16×1 double] NumHoles: [16×1 double] Geometry: "polygon" CoordinateSystemType: "geographic" GeographicCRS: [1×1 geocrs]
us_states.LabelLat % third column
ans = 51×1
32.2827 64.6097 34.3451 34.8350 36.8223 39.0295 41.5106 39.1071 28.3914 32.5803
us_states.(4) % 4th column
ans = 51×1
-86.9206 -152.4593 -112.0705 -91.8861 -119.6633 -105.5440 -72.7627 -75.4942 -82.8483 -83.0864
  7 Comments
Chad Greene
Chad Greene on 2 Nov 2022
This is so frustrating. I don't understand why these new functions have been designed to prevent users from accessing the data we're trying to analyze.

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Chad Greene
Chad Greene on 8 Nov 2022
@Sergey Kostrukov I think I found a working solution. The m_shaperead function in M_Map can handle PolygonZ and PolyLineZ data.
  1 Comment
Sergey Kostrukov
Sergey Kostrukov on 11 Nov 2022
I didn't know about existence of M_Map and it looks amazing! Thank you very much.

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