Saving results from for loop as a vector in r

问题:

I have a rather simple question.

I have the following code:

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

How do I save the results as a vector?

If I try

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

Then call my_vector, I get Null.

回答1:

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.

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

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

回答2:

Following form can also be used:

> my_vector = c()
> for(i in 1:5)       my_vector[length(my_vector)+1] = i
> my_vector
[1] 1 2 3 4 5

回答3:

Alternatively

my_vector = c()
for(i in 1:5){my_vector=c(my_vector,i)}
my_vector