Do a union of polygons and add the associated values for overlapping coordinates

I have 6 matrices of lat, Lon and power values. 3 of them have the same size for lat, lon and power. The other 3 have the same matrix size for lat, lon and power. But different size from the other coordinates. So they both form a polygon would power values but one polygon is bigger and there some overlap. I wanted to do a union between the coordinates and where ever the lat and lon overlap, add the power values together.Since the data are matrices, I tried to convert them into vectors to do a polyshape of lats and lons and do a union after. But that does not seem to work. Well I don’t know for sure because one of the matrices is too big and took forever to be converted into a vector.

    Poly1 =polyshape(lat1,lon1); Poly2 = polyshape(lat2,lon2); polyout =union(Poly1,Poly2);

Since polyshape function does not take a 3rd variable I have not figured how to add the power values together for overlapping coordinates. Is there any other approach I can take to achieve that.

[Simon Chan]

Try function inpolygon

[Mini Me]

Thanks @Simon Chan, I am not only checking the overlap, I am also doing the union of the polygon. In places where they don’t overlap those coordinates would need to be added to a new polygon so to speak.

[Simon Chan]

You may add up the power values together for same coordinates by creating a table and using function outerjoin.

Then you may extract the combined coordinates at the end to form the overlapped polygon.

However, I am not sure how efficient is the code for large matrix.

lat1 = [2 2 3 4 5 5 6];
lon1 = [2 5 6 7 5 2 1];
power1 = [4 10 6 12 3 5 8];
T1 = table([lat1',lon1'],power1','VariableNames',{'Coord' 'Apower'})    % Table for 1st polygon

T1 = 7×2 table
    Coord     Apower
    ______    ______

    2    2       4  
    2    5      10  
    3    6       6  
    4    7      12  
    5    5       3  
    5    2       5  
    6    1       8  

lat2 = [2 5 6 8 3];
lon2 = [4 2 1 8 8];
power2 = [2 7 6 5 3];
T2 = table([lat2',lon2'],power2','VariableNames',{'Coord' 'Bpower'})    % Table for 2nd polygon

T2 = 5×2 table
    Coord     Bpower
    ______    ______

    2    4      2   
    5    2      7   
    6    1      6   
    8    8      5   
    3    8      3   

[T,ileft,~] = outerjoin(T1,T2);
indexleft = find(ileft);
Coord = zeros(size(T,1),2);                                             % Extract the coordinates
for k = 1:size(T,1)
    if ismember(k,indexleft)
        Coord(k,:) = T.Coord_T1(k,:);                                   % Coordintes can be found in 1st polygon
    else
        Coord(k,:) = T.Coord_T2(k,:);                                   % Coordinates only appear in 2nd polygon
    end
end
combinepower = sum([T.Apower,T.Bpower],2,'omitnan');                    % Combine power
S = table(Coord,combinepower)

S = 10×2 table
    Coord     combinepower
    ______    ____________

    2    2          4     
    2    4          2     
    2    5         10     
    3    6          6     
    3    8          3     
    4    7         12     
    5    2         12     
    5    5          3     
    6    1         14     
    8    8          5     

warning off;
pgon1 = polyshape(lat1,lon1);
pgon2 = polyshape(lat2,lon2);
subplot(2,2,1)
plot(pgon1);
hold on
plot(pgon2);
title('Separate polygons')
x = Coord(:,1);
y = Coord(:,2);
k = boundary(x,y);
pgon=polyshape(x(k),y(k));
subplot(2,2,2)
plot(pgon);
title('Combined Coordinates')
subplot(2,2,3)
polyout = convhull(pgon);
plot(polyout)
title('Convex hull of polygon')

[Mini Me]

Thanks for your answer. I added union(pgon) as well. But it takes forever to run.

[Juan Jiménez]

Nice!