如何为我的 for 循环修复一个错误？答案

【问题标题】：How do I fix an off by one error for my for loop?如何为我的 for 循环修复一个错误？
【发布时间】：2020-02-05 10:10:06
【问题描述】：

我遇到了 for 循环的问题。它给了我“一个错误”。我确实计算了观察结果，确实是一次。我该如何解决？

代码：

delta = seq(0,1,0.05)
delta2 = seq(0,1,0.01)
delta3 = seq(0,1,0.001)

price1 = rep(1,length(delta))
price2 = rep(1,length(delta2))
price3 = rep(1,length(delta3))

for(i in 2:length(delta)){
  price1[i] = price1[i-1]+price1[i-1]*rnorm(1)*sqrt(delta)
  price1[i+1] = price1[i] + i
  print(price1[i+1])
}


plot(delta,price1[i+1], type = "l") #Error occurs here

for(i in 2:length(delta2)){
  price2[i] = price2[i-1] + price2[i-1]*rnorm(1)*sqrt(delta2)
  price2[i] = price2[i] + i
  print(price2[i])
}

plot(delta2, price2[i], type = "l") #error here

for(i in 2:length(delta3)){
  price3[i] = price3[i-1] +  price3[i-1]*rnorm(1)*sqrt(delta3)
  xprice3[i] = price3[i] + i
  print(price3[i])
}

plot(delta3, price3[i], type = "l") #error here

错误状态：

xy.coords(x, y, xlabel, ylabel, log) 中的错误： “x”和“y”长度不同

【问题讨论】：

标签： r for-loop

【解决方案1】：

您实际上并不需要循环，但这就是您要寻找的吗？

delta = seq(0,1,0.05)
delta2 = seq(0,1,0.01)
delta3 = seq(0,1,0.001)

price1 = rep(1,length(delta))
price2 = rep(1,length(delta2))
price3 = rep(1,length(delta3))

for(i in 2:length(delta)){
  price1[i] = price1[i-1]+price1[i-1]*rnorm(1)*sqrt(delta[i])
  price1[i] = price1[i] + i
  print(price1[i])
}


plot(delta,price1, type = "l") #Error occurs here

for(i in 2:length(delta2)){
  price2[i] = price2[i-1] + price2[i-1]*rnorm(1)*sqrt(delta2[i])
  price2[i] = price2[i] + i
  print(price2[i])
}

plot(delta2, price2, type = "l") #error here

for(i in 2:length(delta3)){
  price3[i] = price3[i-1] +  price3[i-1]*rnorm(1)*sqrt(delta3[i])
  price3[i] = price3[i] + i
  print(price3[i])
}

plot(delta3, price3, type = "l") #error here

【讨论】：

【解决方案2】：

您可能正在寻找：

delta = seq(0,1,0.05)
delta2 = seq(0,1,0.01)
delta3 = seq(0,1,0.001)

price1 = rep(1,length(delta))
price2 = rep(1,length(delta2))
price3 = rep(1,length(delta3))

for(i in 2:length(delta)){
   price1[i] = price1[i-1]+price1[i-1]*rnorm(1)*sqrt(delta[i])
}
plot(delta,price1, type = "l")


for(i in 2:length(delta2)){
   price2[i] = price2[i-1]+price2[i-1]*rnorm(1)*sqrt(delta2[i])
}
plot(delta2,price2, type = "l")

for(i in 2:length(delta3)){
  price3[i] = price3[i-1]+price3[i-1]*rnorm(1)*sqrt(delta3[i])
}
plot(delta3,price3, type = "l")

【讨论】：

仍然出现错误。更新：没关系。我的代码分为 3 个单独的块。这是其中的一部分。
非常感谢！