Without your second matrix, it is necessary to create data to test code.
It is necessary to ‘close’ the polygon created by the curve so that the inpolygon function will work. I make no guarantees that this will work with your matrix, so you will have to experiment with that.
This works with my test data:
Fr_2=0:0.01:5;
r_theoric=zeros(1,length(Fr_2));
for i=1:length(Fr_2)
r_theoric(i)=sqrt(27*((Fr_2(i)^2)/((2+Fr_2(i)^2)^3)));
end
R=[r_theoric;Fr_2];
R(:,end+1) = [R(1,1); R(2,end)]; % <— Necessary To Complete The Polygon
[Rmax,idx] = max(R,[],2);
another_matrix = bsxfun(@times, rand(50, 2), [5 1]); % Create Data
Below = inpolygon(another_matrix(:,1), another_matrix(:,2), R(2,:), R(1,:)); % Logical Vector
Left = (another_matrix(:,1) < R(2,idx(1))) & ~Below; % Logical Vector
Right = ~Below & ~Left; % Logical Vector
figure
plot(R(2,:), R(1,:))
hold on
plot(another_matrix(Below,1), another_matrix(Below,2), 'pb')
plot(another_matrix(Left,1), another_matrix(Left,2), 'pg')
plot(another_matrix(Right,1), another_matrix(Right,2), 'pm')
hold off
grid
The plot may not be required for your code. It demonstrates that the code works here.
