what does this code mean ?

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

[Rik]

Have a read here (or here for more general advice). It will greatly improve your chances of getting an answer.

What is your question? A line by line explanation?

[Karn Vadaliya]

Actually I have understood the code by myself. All I need now is to know the Matlab alternative for estimateRigidTransform() and transformPoint3d() as these are in available in python ?

[Torsten]

https://de.mathworks.com/matlabcentral/fileexchange/24484-geom3d?focused=7621243&tab=function

https://de.mathworks.com/matlabcentral/fileexchange/25746-kabsch-algorithm

[Karn Vadaliya]

The Kabsch Algorithm gives weird result.

For example I have a set of points (3x3)

setA= [ 8 4 6, 4 6 8, 6 8 4]

after applying r rotation where r= [1 0 0, 0 0.5 0, 0 0 1]

I get setB=setA*r=[8 2 6, 4 3 8, 6 4 4]

so when I do U=Kabsch(setA,setB) I get

U=

[ 0.5651 -0.5325 -0.6302,

0.1846 0.8260 -0.5325,

0.8041 0.1846 0.5651 ]

shouldn't i get U=r in output ?

how come these values of U and what does they mean ?

[Torsten]

r is not a rotation.

[Karn Vadaliya]

Then what is it ?

[Torsten]

https://en.wikipedia.org/wiki/Scaling_(geometry)