Loop / indexing query in MATLAB -

i have matlab code want use find output 50 sources randomly placed inside grid , summed; @ moment can work 1 source; code this;

%required constants ro = 5*10^-6; po = 40; = 5.9336*10^-6; d = 2*10^-9; f = 2.6835*10^-7; mult = a/(4*f*d); rc = 6.0260e-05 pop = 5:1:495;   %initialise 500 x 500 array 0 pp = zeros(500,500);    = 1;   while < 2      x(i) = randsample(pop,1);     y(i) = randsample(pop,1);  %randomly selections x,y point on grid - below if loop sets boundary of %+/70     %microns point examine. min lower point in x , y 1, max 500;          if x(i) - 70 > 0 && x(i) + 70 <= 500 && y(i) - 70 > 0 && y(i) + 70 <= 500          xb(i) = x(i) - 70;         xu(i) = x(i) + 70;          yb(i) = y(i) - 70;         yu(i) = y(i) + 70;      elseif x(i) - 70 < 0 && x(i) + 70 <= 500 && y(i) - 70 > 0 && y(i) + 70 <= 500          xb(i) = 1;         xu(i) = x(i) + 70;          yb(i) = y(i) - 70;         yu(i) = y(i) + 70;      elseif x(i) - 70 > 0 && x(i) + 70 > 500 && y(i) - 70 > 0 && y(i) + 70 <= 500          xb(i) = x(i) - 70;         xu(i) = 500;          yb(i) = y(i) - 70;         yu(i) = y(i) + 70;      elseif x(i) - 70 > 0 && x(i) + 70 <= 500 && y(i) - 70 < 0 && y(i) + 70 <= 500          xb(i) = x(i) - 70;         xu(i) = x(i) + 70;          yb(i) = 1;         yu(i) = y(i) + 70;      elseif x(i) - 70 > 0 && x(i) + 70 <= 500 && y(i) - 70 > 0 && y(i) + 70 > 500          xb(i) = x(i) - 70;         xu(i) = x(i) + 70;          yb(i) = 1;         yu(i) = 500      end       %now test boundaries established, use our equation source....         xm = xb:xu         ym = yb:yu             h(xm,ym) = (sqrt((xm - x).^2 + (ym - y).^2))*10^-6;             %h distance; if beyond rc, source 0             if  h(xm,ym) > rc                  pp(xm,ym) = 0;             elseif  h(xm,ym) < ro                 pp(xm,ym) = po;             else                 pp(xm,ym) = po + mult.*(h(xm,ym).^2 - ro^2 - 2.*rc^2.*log(h(xm,ym)./ro));             end         end     end     = + 1 end 

this works 1 source; code produces single source perfectly. i'm running trouble trying generalise upwards while < 51 ; basically, want modify code 500 x 500 matrix pp created each run of while loop, , instead of over-writing previous ones, these pps summed sources.

i tried modifying h , pp etc functions of i,xm,ym etc didn't seem work me - suggestions / examples of how might this? thanks!

i don't have matlab in front of me, atm, think should work. didn't bother checking if xm or ym negative or 0 or greater 500.

for creating 500 x 500 x 51 pp, do...

this maintain running sum.

pp = zeros([500 500 51]); % removed brevity  i=1:51 %instead of while, less efficient     % removed brevity     xm = xb:xu         ym = yb:yu             h(xm,ym) = (sqrt((xm - x).^2 + (ym - y).^2))*10^-6;             %h distance; if beyond rc, source 0             if  h(xm,ym) > rc                  pp(xm,ym,i) =  0;             elseif  h(xm,ym) < ro                 pp(xm,ym,i) = po;             else                 pp(xm,ym,i) =mult.*(h(xm,ym).^2 - ro^2 - 2.*rc^2.*log(h(xm,ym)./ro));             end         end     end end 

this gives 500 x 500 x 51 matrix pp. given 500x500 can extracted using pp(:,:,index). sum can obtained sum(pp,3)