i should only count the shadow if ashadow>15, how do i do that? also the lengthofshadow only changes for the day number and not the minute of the day, how to solv this?

         close all
clear all
h=[1:24];%hours in day
m=[1:14400];%minutes in day
n_param=5;
n=[1:365];%days in year
az=0.0001; % degrees  %a=0,001 , because a is near zero during sunrise and sunset.
ndec=355; %21 december is de 335e dag van het jaar
njul=202; %21 juli is de 202e dag van het jaar
p=52.3667; %altitude amsterdam
heigthblock=25; %heigth of the block in mETER
sino=zeros(1,365);
max_loops = 100;      
for N=n
    
[n,h]=meshgrid(n,h);

      wh=(h+12)*(pi/12); %OPDRAcht 4
      sinoaz=-23.45*(pi/180)*cos(((2*pi)/365)*(10+n));
     oaz=asin(sinoaz);
    sinashadow=cos(oaz).*cosd(wh).*cosd(p)+sinoaz.*sind(p);
     ashadow=asin(sinashadow);
  %sinAshadow=(sind(wh).*cos(oaz))/sinashadow;
    %Ashadow=asind(sinAshadow);
    
       %Tan(a)=overstaande/aanliggende=height block/lenth shadow
    %lenth shadow=heigth block/Tan(a)
    lenthofshadow=heigthblock./(tan(ashadow));
    
    surf(n,h,lenthofshadow)

   while 15<ashadow||ashadow
    n_loop=n_loop+1;
    if (n_loop >= max_loops)
        disp('exceeded max number of loops') 
           break 
    end
    end
end