%This is a function for resource dynamics of nospec species and one resource
function n = res1(nospec,specpara,supply,loss,lag,nostep)
% species parameters
% growth: growth per unit resource
% uptake: uptake per unit growth
% mortality
% n0 initial size

%resource parameters:
%           supply: resource supply 
%           loss: rate at which resource is removed
%           lag after how many steps the species is introduced

for i=1:nospec
  growth =specpara(:,1);
  uptake=specpara(:,2);
  mortality=specpara(:,3);
  n0=specpara(:,4);
end

if (lag > 0)
   x1=[zeros(nospec,1)'];
else
   x1=[n0'];
end


resource =[supply];

for t=1:nostep
    
   
    for i=1:nospec
       if (t > lag+1)
          xtemp(i)= x1(t,i) + x1(t,i).*(growth(i).*resource(t) - mortality(i));
          if xtemp(i)<0
             xtemp(i) = 0;
          end
       elseif (t==lag+1)
          xtemp(i) = n0(i);
       else
          xtemp(i) = 0;
       end 
    end
    restemp= resource(t) + supply - loss*resource(t) - sum(growth.*uptake.*x1(t,:)').*resource(t);
    if restemp < 0
       restemp=0;
    end 
  

   resource =[resource restemp];
   x1 = [x1; xtemp];
end
n = [resource;transpose(x1)];