如何使用for循环制作向量 [英] How to make a vector using a for loop

问题描述

我对R（以及一般的编程）非常陌生，并且我已经坚持了几天这个（可能非常简单）的问题...

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...

如何使用 for 循环来生成向量 3 6 12 24 48 96 192 384 768 ？

How would one make the vector 3 6 12 24 48 96 192 384 768 with a for loop?

到目前为止，我设法提出的是：

All I've managed to come up with so far is something along the lines of:

x=numeric()
for (i in 1:8) (x=2*i[-1])

然而，这不起作用。我认为其中一个主要问题是我不明白如何在一个序列中索引数字。

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.

如果有人能指出我正确的方向那将是这样的一个很好的帮助！

If anyone could point me in the right direction that would be such a great help!

推荐答案

好的，你需要知道的第一件事是如何将东西附加到矢量。你想要的功能就足够了追加：

Okay, the first thing you need to know is how to append things to a vector. Easily enough the function you want is append:

x <- c(1, 2)
x <- append(x, 3)

将使向量x包含（1,2,3）就像你已经完成 x< - （1,2,3）。接下来你需要意识到的是，目标向量的每个成员都是前一个成员的两倍，这在for循环中很容易实现

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

n <- 1
for (i in 1:8)
{
    n <- n*2
}

将使每个循环加倍。显然，您可以通过在 n< - n * 2 语句之前或之后放置其他语句，将其用于加倍或未加倍的形式。

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.

希望你可以将这两个东西放在一起，形成你想要的循环。

Hopefully you can put these two things together to make the loop you want.

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