Fill inside a polygon with a color

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BN
BN am 3 Mai 2020
Kommentiert: Patrick Laux am 13 Jul. 2021
Dear all,
I want to fill a polygon that I readed from shapefile with blue in order to visualzing it as lake. I searched alot and tried:
S2 = shaperead('lake.shp');
polygonwater1_y = S2(1).X;
polygonwater1_x = S2(1).Y;
fill (polygonwater1_y,polygonwater1_x,'b')
And:
patch (polygonwater1_y,polygonwater1_x,'b')
But as you can see below, unfortunately, it doesn't fill:
Do you know how can I do to fill it?
Thank you
  2 Kommentare
KSSV
KSSV am 3 Mai 2020
Atatch the data.
BN
BN am 3 Mai 2020
Dear KSSV
I attached data here. There is my shapefile containing 3 lakes. I want to fill all of them by blue.
Thank you.

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Akzeptierte Antwort

KSSV
KSSV am 3 Mai 2020
Bearbeitet: KSSV am 3 Mai 2020
It happned because, your region have multiple regions inside and they have NaN's.
shfile = "Lakes/lakes.shp" ;
S = shaperead(shfile) ;
N = length(S) ;
x = S(3).X ; y = S(3).Y ; % Picked the 3rd region
idx = find(isnan(x)) ; % find positions of NaNs
idx = [1 idx length(x)] ; % append first and last position
figure
hold on
for i = 1:length(idx)-1
pos = idx(i):idx(i+1) ; % gEt the required position
xi = x(pos) ; yi = y(pos) ; % GEt the corodinates
% Remove NaN's
xi(isnan(xi)) = [] ;
yi(isnan(yi)) = [] ;
patch(xi,yi,'b') ; % color the area
end
  4 Kommentare
KSSV
KSSV am 26 Aug. 2020
Because the user wanted the third region.
Patrick Laux
Patrick Laux am 13 Jul. 2021
smart procedure

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Weitere Antworten (1)

Steven Lord
Steven Lord am 26 Aug. 2020
Another way to plot and work with this data is to create a polyshape for each region.
S = shaperead('lakes.shp');
for k = 1:numel(S)
P(k) = polyshape(S(k).X, S(k).Y); % This will issue a warning each time
end
plot(P(3), 'FaceColor', 'r')
% Or plot all of them
figure
plot(P)
Some of the functions for working with polyshape objects may be of use to you. For example, computing the area of the polyshape agrees pretty well with the Shape_Area from the shape file.
[area(P(3)); S(3).Shape_Area; area(P(3))-S(3).Shape_Area]
  2 Kommentare
Ishaan Chauhan
Ishaan Chauhan am 18 Feb. 2021
Do you know of any ways to code to ignore the warnings?
Patrick Laux
Patrick Laux am 13 Jul. 2021
warning off

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