本人也是刚接触代码，这也是第一次写，比较简陋，请见谅。问题是最后一个for循环每次运行只会跑一遍，导致price与profit的数据只能出现前面几个，后面的数据无法跑出来，请问问题在哪里，怎么解决？

K=50

S0=50;        #initial price S0

mu=0.04;    #drift mu

sigma=0.1;  # volatility sigma

T=1;           #1 year

NSteps=20;

NReps=2;

SPaths = matrix(NA,NReps,NSteps+1);

d1 = matrix(NA,NReps,NSteps+1);

d2 = matrix(NA,NReps,NSteps+1);

N1 = matrix(NA,NReps,NSteps+1);

N2 = matrix(NA,NReps,NSteps+1);

c = matrix(NA,NReps,NSteps+1);

qty = matrix(NA,NReps,NSteps+1);

price = matrix(NA,NReps,NSteps+1);

profit = matrix(NA,NReps,NSteps+1);

QTY = matrix(NA,NReps,NSteps+1);

SPaths[,1] = S0;

dt = T/NSteps

nudt = (mu-0.5*sigma^2)*dt

sidt = sigma*sqrt(dt)

for (i in 1:NReps){

  for(j in 1:NSteps){

   SPaths[i,j+1] = SPaths[i,j]*exp(nudt + sidt*rnorm(1))

   time=(NSteps-j+1)/NSteps

   d1[i,j]=(log(SPaths[i,j]/K)+(mu+0.5*sigma^2)*time)/(sigma*sqrt(time))

   d2[i,j]=(log(SPaths[i,j]/K)+(mu-0.5*sigma^2)*time)/(sigma*sqrt(time))

   N1[i,j]=pnorm(d1[i,j])

   N2[i,j]=pnorm(d2[i,j])

   c[i,j]=SPaths[i,j]*N1[i,j]-K*exp(-mu*time)*N2[i,j]

   QTY[i,j]=1000*N1[i,j]

  }

}

qty[,1]=SPaths[,1]*QTY[,1];

price[,1]=qty[,1];

profit[,1]=(exp(mu/NSteps)-1)*price[,1];

for (i in 1:NReps){

  for(j in 1:NSteps){

   qty[i,j+1]=(QTY[i,j+1]-QTY[i,j])*SPaths[i,j+1]

   price[i,j+1]=price[i,j]+profit[i,j]+qty[i,j+1]

   profit[i,j]=(exp(mu/NSteps)-1)*price[i,j]

  }

}