MATLAB: I want the points that located in a certain polygon

MATLABpolygon

Hey,

I have 92 points. Each point has latitude and longitude. On the other hand, I have a shape file consist of six different polygons. I want to know which point located in which polygon. For example, I want to have all points located in the first polygon.

filename ='Basin1_waterse_ir.shp'
S = shaperead(filename)
S = 
  6×1 struct array with fields:
    Geometry
    BoundingBox
    X
    Y
    DEGREE1
    HECTARES
    AREA
    PERIMETER
    x0xE40xC70xE3
    ACRES

Thank you all.

Best Answer

You use different order of lan/lot. Change places in red squares

Related Solutions

MATLAB: Create a box around points and use in inpolygon

load("polygon1_x.mat") ; 
load("polygon1_y.mat") ; 
load("lon.mat") ; 
load("lat.mat") ; 
% remove Nan's from the data 
xv = polygon1_y ; yv = polygon1_x ; 
xv(isnan(xv)) = [] ;
yv(isnan(yv)) = [] ;
%
loncoord = zeros([],1) ; 
latcoord = zeros([],1) ;
count = 0 ; 
for i = 1:length(lon)
  i
    % make grid around (lon,lat)
  x = lon(i)-0.5:0.5:lon(i)+0.5 ; 
  y = lat(i)-0.5:0.5:lat(i)+0.5 ; 
  [X,Y] = meshgrid(x,y) ; 
  [in,on] = inpolygon(X(:),Y(:),xv,yv);         % Logical Matrix
  inon = in | on;                                             % Combine ‘in’ And ‘on’
  idx = find(inon(:));                                        % Linear Indices Of ‘inon’ Points
  
  if any(idx)
    count = count+1 ; 
    loncoord(count) = lon(i);                                        % Y-Coordinates Of ‘inon’ Point
    latcoord(count) = lat(i) ;   
  end
end
plot(polygon1_y,polygon1_x,'b')
hold on
plot(loncoord,latcoord,'*r')

MATLAB: Select points inside a polygon

Here is the code using POLYSHAPE

load('Points.mat')
load('polygon1_x.mat')
load('polygon1_y.mat')
lat = Points.lat;                                         % x of points = lat
lon = Points.lon;                                         % y of points = lon
wpixel = 0.5;
hpixel = 0.5;
pixel0 = [-1  1 1 -1;
          -1 -1 1  1]' .* [wpixel, hpixel]/2;
Island = polyshape([polygon1_y(:) polygon1_x(:)]);
for k=1:length(lat)
    poly = polyshape([lon(k) lat(k)]+pixel0);
    Ik = intersect(poly,Island);
    isin = ~isempty(Ik.Vertices);
    pixel(k).poly = poly;
    pixel(k).isin = isin;
end
% Index of pixel that intersect with Island
idxin = find([pixel.isin]) % <=== HERE IS THE INDEX YOU NEED 
% Graphical output
close all
plot(Island)
hold on
for k=1:length(pixel)
    if pixel(k).isin
        color = 'r';
    else
        color = 'w';
    end
    plot(pixel(k).poly, 'FaceColor', color);
end
axis equal

Best Answer

Related Solutions

MATLAB: Create a box around points and use in inpolygon

MATLAB: Select points inside a polygon

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