Display order of objects in vector in R

Let's say I create a simple vector:

x <- seq(1, 50, by = 5)

x <- seq(1, 50, by = 5)

Then I might want to display its contents to see which item is the 7th:

print(x)

[1] 1 6 11 16 21 26 31 36 41 46


Is there a simple way to display the contents such that each item is numbered?

[1] 1, [2] 6, [3] 11, etc.

[1] 1, [2] 6, [3] 11, etc.

3 Answers
3

One simple option is to column-bind a counter next to the original vector:

cbind(1:length(x), x)


An elegant way might be to use ?names.

?names

x <- seq(1, 50, by = 5)
names(x) <- seq_along(x)
x
1 2 3 4 5 6 7 8 9 10
1 6 11 16 21 26 31 36 41 46


I assume you're asking how to modify print to include the index of every element of a vector x.

print

x

Here is a possibility

x <- seq(1, 50, by = 5)

cat(sapply(seq_along(x), function(i) (sprintf("[%i] %i", i, x[i]))), "n")
#[1] 1 [2] 6 [3] 11 [4] 16 [5] 21 [6] 26 [7] 31 [8] 36 [9] 41 [10] 46


Or you could define a custom my.print function that nicely wraps lines every nmaxth entry for long vectors

my.print

nmax

my.print <- function(x, nmax = 6) {
os <- 0
while (length(x) > 0) {
cat(sapply(seq_along(x[1:min(length(x), 6)]), function(i)
sprintf("[%i] %i", i + os, x[i])), "n")
x <- x[-(1:min(length(x), nmax))]
os <- os + nmax
}}

my.print(x)
#[1] 1 [2] 6 [3] 11 [4] 16 [5] 21 [6] 26
#[7] 31 [8] 36 [9] 41 [10] 46


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