Is it possible to vectorize for loop or otherwise make this code more efficient?

Can someone please help with code efficiency? The code is as follows:

 Qx=zeros(Q_xlkm,Q_ylkm);     % Q_xlkm = 201, Q_ylkm = 21
Qy=zeros(Q_xlkm,Q_ylkm);
for i=1:Q_ylkm
    Qx(:,i)=xxQ;     % xxQ= 1x201 vector containing x-coordinates
end
for i=1:Q_xlkm
    Qy(i,:)=yyQ;     % yyQ= 1x21 vector containing y-coordinates
end
  for x=1:101
    for y=1:21
        for z=1:100
            x1=xx(x);      % xx= 1x101 vector containing x-coordinates
            y1=yy(y);      % yy= 1x21 vector containing y-coordinates
            z1=zz(z);      % zz= 1x100 vector containing z-coordinates
            X=Qx-x1;       % 201x21 matrix containing the difference in x for each load and current x-coordinate       
            Y=Qy-y1;       % 201x21 matrix containing the difference in y for each load and current y-coordinate  
            X2=X.^2;       % Elementwise square of x-differences 
            Y2=Y.^2;       % Elementwise square of y-differences
            r_apu=X2+Y2;
            Z=Qz-z1;       % 201x21 matrix containing the difference in z for each load and current z-coordinate  
            Z(Z<1)=1;
            Z2=Z.^2;
            Z3=Z.^3;
            QqZ3=Qq.*Z3;
            r2Z2=r_apu+Z2;
            r2Z2_potenssi=r2Z2.^(-5/2);
            sig=QqZ3.*r2Z2_potenssi;
            dsig=(3/(2*pi))*sig;               % 201x21 Matrix. An element of this matrix is the stress in a point P(x,y,z) due to load Q(x,y,z,q)
            P(x,y,z)=sum(sum(dsig));           % Stress in a point P(x,y,z) due to all loads
        end  
    end
end

The main equation for this code is as follows:

For clarification, the p coordinates are as follows: xx=0:1:100 yy=0:1:20 zz=-10:0.1:-0.1

Q coordinates: xxQ = 0:0.5:100 yyQ = 0:1:20 z-coordinate depends on x,y and is in the range of 0:1

Basically what I want to do is for each x,y,z point in 101x21x100 3D-matrix P, I want to calculate loads from each load with coordinates x,y,z and quantity (defined by 201x21 matrices Qx,Qy,Qz and Qq) and then sum all the loads into each x,y,z point in P. Is there a way to do this more efficiently? Thanks!

[KSSV]

x,y,z point is 101x21x100 or 201X21X100?

[John Chilleri]

You can simplify the first two loops pretty easily,

 for i=1:Q_ylkm
    Qx(:,i)=xxQ;     % xxQ= 1x201 vector containing x-coordinates
 end
 for i=1:Q_xlkm
    Qy(i,:)=yyQ;     % yyQ= 1x21 vector containing y-coordinates
 end

 % Change the above to:

 Qx(:,1:Q_ylkm) = xxQ;
 Qy(1:Q_xlkm,:) = yyQ;

Answer 1

[Image Analyst]

In addition to what John said above, you could do this:

for x=1:101
    x1=xx(x);      % xx= 1x101 vector containing x-coordinates
    for y=1:21
        y1=yy(y);      % yy= 1x21 vector containing y-coordinates
        for z=1:100
            z1=zz(z);      % zz= 1x100 vector containing z-coordinates

You could also call sum() just once:

P(x, y, z) = sum(dsig(:));

Beyond that, I don't know, because I don't really know what this code is doing due to the lack of comments. Please consider adding comments.

[Aatu]

The question has been edited for further clarification.