what does this code mean ?

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Karn Vadaliya on 19 Mar 2019

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https://se.mathworks.com/matlabcentral/answers/450882-what-does-this-code-mean

Commented: Torsten on 25 Mar 2019

function PV=Get_Pivot_Point(PP)
% PP dimension: (no. of observation X 4 [no. of markers] X 3[x,y,z 3-d coordinate of marker] )
pv_tool = squeeze(PP(1,:,:));
%pv_tool=[0 0 0 ; 0 0 50; 0 25 100 ; 0 -25 135];
p_pairs=nchoosek(1:size(PP,1),2);
num_exapmple=10;
whos
pivot_points=[]
for k=1:10
    P1=[];
    P2=[];
    rp=randperm(size(p_pairs,1),num_exapmple)
    rp_a=p_pairs(rp,1);
    rp_b=p_pairs(rp,2);
    for i=1:10 
        P1=[P1 ; squeeze(PP(rp_a(i),:,:))'];
        P2=[P2 ; squeeze(PP(rp_b(i),:,:))'];    
    end
    X=compute_pivot_point(P1,P2);    
    
    tmp_pivot_points=[];
    for j=1:size(PP,1)
        
       [T, Eps] = estimateRigidTransform(pv_tool', squeeze(PP(j,:,:))); % (target, source)
       tmp_pivot_points=[tmp_pivot_points ; transformPoint3d(X',T)];
       
    end
    
    pivot_points=[pivot_points ; mean(tmp_pivot_points)];
       
end
plot3(pv_tool(:,1),pv_tool(:,2),pv_tool(:,3),'r*')
hold on
plot3(pivot_points(:,1), pivot_points(:,2), pivot_points(:,3),'b*')
grid on
axis equal
 
PV.pv_point=median(pivot_points);
PV.pv_tool=pv_tool;
end
function X=compute_pivot_point(P1,P2)
[X, R]  = linsolve([P2-P1],sum([P2.^2-P1.^2], 2)/2);
end