MATLAB: Find edges in a plot

Question

I've been trying for a while to find the following edges on a graph as shown in the picture below

The following code is for the path and plot

path_test=[ 106 20;

107 19;

108 18;

109 17;

110 16;

111 15;

112 14;

113 13;

114 12;

114 11;

114 10;

115 9;

116 9;

117 9;

118 9;

119 9;

120 9;

121 9;

122 9;

123 9;

124 9;

125 9;

126 9;

127 9;

128 10;

129 10;

130 10];

plot(path_test(:,2),path_test(:,1),'b');

I've tried to use islocalmin and ischange as shown bellow

index1=islocalmin(path_test,'FlatSelection','first');

index2=islocalmin(path_test,'FlatSelection','last');

index3=ischange(path_test);

index = [index1 index2 index3];

path_index=[];

for i=1:length(index)

if (any(index(i,:))==1 && all(index(i,:))==0)

path_index = [path_index i];

end

end

figure(11)

plot(path_test(:,2),path_test(:,1),'b');

hold on

plot(path_test(path_index,2),path_test(path_index,1),'rX')

And to use all of these commands alone, but i only get the following points shown in the plot below

With only findlocalmin i get the following

I was woundering if anyone know about a way to find the points of interest?

Answer 1

Better solution

x = path_test(:,2);
y = path_test(:,1);
dangle = diff( diff(y)./diff(x) );
ind = find(abs(dangle) > 0.1)+1;
hold on
plot(x(ind),y(ind),'or')
hold off