将for循环的结果另存为r中的向量 [英] Saving results from for loop as a vector in r

问题描述

我有以下for循环，可打印从1到10的数字:

I have the following for loop which prints numbers from 1 to 10:

for (i in 1:10) {print (i) } 

如何将结果另存为矢量，而不是仅将其打印到控制台?

How do I save the results as a vector, instead of just printing them to the console?

如果我尝试:

my_vector <- for (i in 1:10) {print (i) } 

然后致电my_vector，我得到:

NULL 

推荐答案

调用print始终会将每次迭代的结果打印到控制台.如果保留print命令，则可能会得到不需要的输出.

Calling print will always print the result of each iteration to the console. If you leave in the print command, then you might get unwanted output.

您的主要问题是您没有在for循环之前初始化my_vector.相反，您可以执行以下操作，而不会产生print副作用.

Your main problem is that you did not initialize my_vector before the for loop. You could instead do the following and not get the print side-effect.

my_vector <- vector("numeric", 10L)
for(i in 1:10) my_vector[i] <- i
my_vector
# [1]  1  2  3  4  5  6  7  8  9 10

但是请注意，这与使用sapply进行以下操作相同，但是在这种情况下，您不需要声明，可以将结果分配给向量.

But note that this is just the same as doing the following with sapply, but in this case you need no declaration and you can assign the result to a vector.

my_vector2 <- sapply(1:10, function(x) x)
my_vector2
# [1]  1  2  3  4  5  6  7  8  9 10

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