storing all results in final matrix to save space in matlab when using for loop

coordinates for Points Pi(total 33 in #,11*3 matrix form) are known by combination of x-coord, y-coord, z-coord. Ray1 goes from known points A(x1,y1,z1) to P1(x2,y2,z2).It enters a region of interest at entry point(x3,y3,z3) and comes out through exit point(x4,y4,z4) such that entry and exit points are somewhere between A and P1.Transmission at entry point is known and I am trying to find out transmission at exit point because of attenuation.So, I reach to point,B in ray direction through incremental distance from A and find out transmission at B as I know transmission at entry point. Then I find out transmission at next point C as I know transmission at B. This way I finally find out transmission at exit point.Since I have 33 Pi points (in 3 rows and 11 columns), my final transmission matrix will be 3*11 size. I could the result if I create big matrix for intermediate steps like 'entry_point_coord,exit_point_coord, CT_number' etc. But I only want to store all my results in 'Final_Transmission' matrix. My matlab code is as follows. But I don't get a transmission matrix of required size and also did not get transmission values that I expect to get. Any help to resolve this issue will be appreciated.

A=[x1 y1 z1]

Transmission=1

%  To create Pi points

x_coord=x1:increment:x2; %size 1*11

y_coord=y1:increment:y2; %size 1*3

z_coord=z; %it is constant

x_index=0;

y_index=0;

for i=1:3

y_index=y_index+1;

for j=1:11;

y_index=y_index+1;

Transmission=1

d=sqrt(sum(([x_coord(1,j),y_coord(1,i),z]-[x1,y1,z1]).^2));finding distance between A and Pi
entry_point_coordinate=[x1,y1,z1]+[x_coord(1,j)/d,y_coord(1,i)/d,z/d];

exit_point_coordinate=[x1,y1,z1]+[x_coord(1,j)/1.5*d,y_coord(1,i)/1.2*d,z/d];

x_coordinate_of_interest_point=entry_point_coordinate(1,1):increment:Exit_point_coordinate(1,1);
        y_coordinate_of_interest_point=entry_point_coordinate(1,2):increment:Exit_point_coordinate(1,2);
        z_coordinate_of_interest_pointt=entry_point_on_CT_data_for_ray(1,3):increment:Exit_point_coordinate(1,3);

for k=1:size(x_coordinate_of_interest_point,2);

spatial_coordinate_of_interest_point=[x_coordinate_of_interest_point(1,k) y_coordinate_of_interest_point(1,k) z_coordinate_of_interest_point(1,k)];

CT_number=interp3(....,spatial_coordinate_of_point);%I am fine with interp3 code inputs 

attenuation=.2164*(1+CT_number/1000);% gives att coeff corresponding to CT_number

   density=interp1(.....CT_number);%I am also fine with interp1 code inputs 

   Product=attenuation.*(0.1.*density);

   New_Transmission_Factor=(Transmission_Factor).*(exp(-Product));
          end 
   Final_Transmission(y_index,x_index)=New_Transmission_Factor;
      end 
   end