Question

我一直在试图解决这个问题，但不幸的是我对积分和R都很陌生。任何人都可以帮我弄清楚我在这里做错了什么吗？问题如下： Question 3

到目前为止，这是我的代码：

## Question 3
rm(list=ls())

## a)
X<-(2*(1:20))
X

## b)
Y<-rep(0,20)
Y

## c)
for (k in 1:20){
  Y[k] <- k
  if (k < 12){
    Y[k]<-cos(3*k)
  } else if (k >= 12) {
    integral <- function(t) sqrt(t)
    Y[k]<-integrate(integral, lower = 0, upper = k)
  }
}
Y

这是我运行代码时的输出：

Warning messages:
1: In Y[k] <- integrate(integral, lower = 0, upper = k) :
  number of items to replace is not a multiple of replacement length
2: In Y[k] <- integrate(integral, lower = 0, upper = k) :
  number of items to replace is not a multiple of replacement length
3: In Y[k] <- integrate(integral, lower = 0, upper = k) :
  number of items to replace is not a multiple of replacement length
4: In Y[k] <- integrate(integral, lower = 0, upper = k) :
  number of items to replace is not a multiple of replacement length
5: In Y[k] <- integrate(integral, lower = 0, upper = k) :
  number of items to replace is not a multiple of replacement length
6: In Y[k] <- integrate(integral, lower = 0, upper = k) :
  number of items to replace is not a multiple of replacement length
7: In Y[k] <- integrate(integral, lower = 0, upper = k) :
  number of items to replace is not a multiple of replacement length
8: In Y[k] <- integrate(integral, lower = 0, upper = k) :
  number of items to replace is not a multiple of replacement length
9: In Y[k] <- integrate(integral, lower = 0, upper = k) :
  number of items to replace is not a multiple of replacement length
> Y
[[1]]
[1] -0.9899925

[[2]]
[1] 0.9601703

[[3]]
[1] -0.9111303

[[4]]
[1] 0.843854

[[5]]
[1] -0.7596879

[[6]]
[1] 0.6603167

[[7]]
[1] -0.5477293

[[8]]
[1] 0.424179

[[9]]
[1] -0.2921388

[[10]]
[1] 0.1542514

[[11]]
[1] -0.01327675

[[12]]
[1] 27.71282

[[13]]
[1] 31.24811

[[14]]
[1] 34.92214

[[15]]
[1] 38.72984

[[16]]
[1] 42.66667

[[17]]
[1] 46.72854

[[18]]
[1] 50.91169

[[19]]
[1] 55.21273

[[20]]
[1] 59.62849

当我使用计算器检查结果时，我的b）值似乎不正确，我不知道为什么我收到c）的警告。我也不熟悉积分，所以我不知道我应该对这个问题有什么样的价值观。感谢您提供任何帮助！

Answer 1

问题是，integrate(...)正在为您提供list，并且您希望在向量中替换它。这就是错误。

integral <- function(t) sqrt(t)
result <- integrate(integral, lower = 0, upper = 1)
is(result)
# [1] "integrate" "oldClass" 

result$value
# [1] 0.6666667

这是您的问题的解决方案。你的第二行没有必要。

for (k in 1:20){
  if (k < 12){
    Y[k]<-cos(3*k)
  } else if (k >= 12) {
    integral <- function(t) sqrt(t)
    result <- integrate(integral, lower = 0, upper = k)
    Y[k] <- result$value
  }
}

R中的基本被积累过程

1 个答案: