How do I append to a vector using a `while` loop?

Question

I want to make a vector using a loop.

Here's my R code:

vec_teamCodes <- c()
x <- 0
while (x < 10) {
  append(vec_teamCodes,"Hello")
  x <- x+1
}

But when I run it, vec_teamCodes() remains NULL.

Why? How do I fix my code?

`append` does not assign value to variables in arguments, it creates a new variable. — Bulat, Jun 19 '16 at 21:25
I think you're either looking for `rep('Hello', 10)` or `paste(rep('Hello', 10), collapse = '')` — alistaire, Jun 19 '16 at 21:28
In general you will want to avoid extending vectors in this fashion. Though it works alright in this specific context, it is highly inefficient and will bite you in larger problems. Consider reading [@JoshuaUlrich's answer](http://stackoverflow.com/a/22235924/3358272) to a question on appending to a vector. — r2evans, Jun 19 '16 at 21:31

989 · Accepted Answer · 2016-06-19T21:36:17.283

5

Try this:

vec_teamCodes <- c()
x <- 0
while (x < 10) {
  vec_teamCodes <- c(vec_teamCodes,"Hello")
  # OR
  # vec_teamCodes <- append(vec_teamCodes,"Hello")
  x <- x+1
}


[1] "Hello" "Hello" "Hello" "Hello" "Hello" "Hello" "Hello" "Hello" "Hello" "Hello"

edited Jun 19 '16 at 21:36

answered Jun 19 '16 at 21:23

989

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5
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53

What are you starting with for `vec_teamCodes`? – alistaire Jun 19 '16 at 21:32
@alistaire updated, was clear after seeing OP's question, though. – 989 Jun 19 '16 at 21:37
@Bulat Can you tell me why you edited my answer for for putting `=`? – 989 Jun 19 '16 at 21:39
or `vec_teamCodes <- numeric(0)`; OP should note for the long run that this idiom is inefficient in R. – Ben Bolker Jun 19 '16 at 21:40
@ZheyuanLi: yes, wasn't reading carefully (not much practical difference, but yours is more sensible) – Ben Bolker Jun 19 '16 at 21:41
I guess - http://stackoverflow.com/questions/1741820/assignment-operators-in-r-and – Bulat Jun 19 '16 at 21:41
1

@Bulat: this stylistic difference (`=` vs `<-`) has provoked minor religious wars in R mailing lists before now, so probably best not to modify others' code that way ... – Ben Bolker Jun 19 '16 at 21:42
Ok, I don't mind really ) that would be consistent with the question though, so it is not about the war on style. – Bulat Jun 19 '16 at 21:45
1

@Bulat Well said -> Ben Bolker. – 989 Jun 19 '16 at 21:49

How do I append to a vector using a `while` loop?

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