#This is a function for resource dynamics of nospec species and one resource
res1 = function(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

  if (nospec > 1) {
    growth =specpara[,1];
    uptake=specpara[,2];
    mortality=specpara[,3];
    n0=specpara[,4];
  }
  else {
    growth =specpara[1];
    uptake=specpara[2];
    mortality=specpara[3];
    n0=specpara[4];
    
  }

  for (i in 1:nospec) {
    x1 = matrix(rep(0,(nostep+1)*nospec),ncol = nospec) 
    if (lag == 0)
      x1[1,]=n0 ; 
  }


  resource =rep(NA,nostep+1)
  resource[1] = supply;

  for (t1 in 1:nostep) {
     xtemp = rep(0,nospec)
     for (i in 1:nospec) {
       if (t1 > lag+1) {
          xtemp[i]= x1[t1,i] + x1[t1,i]*(growth[i]*resource[t1] - mortality[i]);
          if (xtemp[i]<0) {
             xtemp[i] = 0;
          }
       }
       else {
         if (t1==lag+1) 
           xtemp[i] = n0[i]
         else
           xtemp[i] = 0
       } 
     }
     restemp = resource[t1] + supply - loss*resource[t1] - sum(growth*uptake*x1[t1,])*resource[t1]; #testovat
     if (restemp < 0)
       restemp=0;

    resource[t1+1] =  restemp; 
    x1[t1+1,] = xtemp
  }
  cbind(resource,x1)
}