saving data that calculates in the loop

Question

Laura 2016-6-6

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https://ww2.mathworks.cn/matlabcentral/answers/288030-saving-data-that-calculates-in-the-loop

编辑： Laura 2016-6-6

Hi everyone

I want to save the value 'ang' in my code as shown below. I want to look for particles that in the distance from 'rmin' to 'rmin+dr' and calculate the angle for it. I dont want to calculate the angle for the same particles such as when j=1,k=1, j=2,k=2, and so on. First problem, the way that I set up in my code ang(j,k), the data(ang) will give 0 degree for j=1,k=1, and so on. Second problem, when the particle distance is not in the range of rmin to rmin+dr, the code also fills with 0 degree. I do not want both problems to be happened.

I was thinking to delete zero components but it would not be right because if the particles align on horizontal (has the same value of y), then angle will be zero and this is ok.

Please helps. Thanks

 clear all
 close all
% Minimum value of r is one particle diameter
rmin=[0.0944069743882630];
   % Define the shell thickness (dr).
   dr=rmin/2;
   XTtrue=[-.35 -.25 -.38 -.42 -.3];
   YTtrue=[ -.28 -.22 -.18 -.35 -.37];
        % Loop all number of the particles.
        for j=1:5
            for k=1:5
            Count=0;
            if j~=k
                % distance between x position
                sepx=(XTtrue(1,k)-XTtrue(1,j));
                % distance between y position
                sepy=(YTtrue(1,k)-YTtrue(1,j));
                % Separation between the center  to-center of any particles.
                dist= sqrt(sepx^2 +sepy^2);
                % angle between particle-particle respects to flow x-direction 
                % atan2d is invert tangent and use to find angle in degree
                % unit. Because atan2d returns angle between -180 to 180
                % degree. Mod(atan2d,360) to account angle between 0-360. 
                % Count the number of particles inside the distance r and r +dr
                if (dist>= rmin && dist<=(rmin+dr) )
                    ang(j,k)=mod(atan2d(sepy,sepx),360);
                end
            end
        end
    end