I'm very new to R (and programming in general) and I've been stuck on this (probably very easy) question for a few days...
我对R(以及一般的编程)非常陌生，我已经被这个(可能非常简单的)问题困扰了好几天……
How would one make the vector 3 6 12 24 48 96 192 384 768 with a for loop?
如何使向量3 6 12 24 48 96 192 384 768带有一个for循环?
All I've managed to come up with so far is something along the lines of:
到目前为止，我所能想到的都是:
x=numeric()
for (i in 1:8) (x=2*i[-1])
However, that doesn't work. I think one of the main problems is that I don't understand how to index numbers in a sequence.
然而,这是行不通的。我认为主要的问题之一是我不知道如何在一个序列中索引数字。
If anyone could point me in the right direction that would be such a great help!
如果有人能给我指出正确的方向，那将是一个很大的帮助!
3 个解决方案
#1
14
Okay, the first thing you need to know is how to append things to a vector. Easily enough the function you want is append:
首先你要知道的是如何把东西附加到向量上。很容易，你想要的功能是追加:
x <- c(1, 2)
x <- append(x, 3)
will make the vector x contain (1, 2, 3) just as if you'd done x <- (1, 2, 3). The next thing you need to realise is that each member of your target vector is double the one before, this is easy to do in a for loop
将使向量x包含(1,2,3)就像你做了x <-(1,2,3)一样。接下来你需要意识到的是目标向量的每个元素都是之前的两倍，这在for循环中很容易做到
n <- 1
for (i in 1:8)
{
n <- n*2
}
will have n double up each loop. Obviously you can use it in its doubled, or not-yet-doubled form by placing your other statements before or after the n <- n*2 statement.
将会有n倍的每个循环。显然，您可以将其他语句放在n <- n*2语句之前或之后，来使用它的双精度或非双精度形式。
Hopefully you can put these two things together to make the loop you want.
希望你能把这两件事放在一起来做你想要的循环。
#2
14
x=c()
x[1] = 3
for (i in 2:9) {
x[i]=2*x[i-1]
}
#3
2
Really, folks. Stick with the solution hiding in Arun's comment.
真的,人。坚持Arun评论中隐藏的解决方案。
Rgames> 3*2^(0:20)
[1] 3 6 12 24 48 96 192 384 768
[10] 1536 3072 6144 12288 24576 49152 98304 196608 393216
[19] 786432 1572864 3145728
#1
14
Okay, the first thing you need to know is how to append things to a vector. Easily enough the function you want is append:
首先你要知道的是如何把东西附加到向量上。很容易，你想要的功能是追加:
x <- c(1, 2)
x <- append(x, 3)
will make the vector x contain (1, 2, 3) just as if you'd done x <- (1, 2, 3). The next thing you need to realise is that each member of your target vector is double the one before, this is easy to do in a for loop
将使向量x包含(1,2,3)就像你做了x <-(1,2,3)一样。接下来你需要意识到的是目标向量的每个元素都是之前的两倍，这在for循环中很容易做到
n <- 1
for (i in 1:8)
{
n <- n*2
}
will have n double up each loop. Obviously you can use it in its doubled, or not-yet-doubled form by placing your other statements before or after the n <- n*2 statement.
将会有n倍的每个循环。显然，您可以将其他语句放在n <- n*2语句之前或之后，来使用它的双精度或非双精度形式。
Hopefully you can put these two things together to make the loop you want.
希望你能把这两件事放在一起来做你想要的循环。
#2
14
x=c()
x[1] = 3
for (i in 2:9) {
x[i]=2*x[i-1]
}
#3
2
Really, folks. Stick with the solution hiding in Arun's comment.
真的,人。坚持Arun评论中隐藏的解决方案。
Rgames> 3*2^(0:20)
[1] 3 6 12 24 48 96 192 384 768
[10] 1536 3072 6144 12288 24576 49152 98304 196608 393216
[19] 786432 1572864 3145728