R equivalent of Python's range() function

Question

Is there an R equivalent to Python's range function?

In Python I can do this:

for i in range(1, 4):
    print(i)

1
2
3

and especially this:

for i in range(1, 0):
    print(i)

# prints nothing!

Meanwhile in R:

> 1:0

[1] 1 0

also

> c(1:0)

[1] 1 0

and

> seq(from=1, to=0)

[1] 1 0

I need a function that given as input a min and a max returns a vector of increasing integers from min to max s.t. if max < min returns an empty vector.

This question on SO is different from mine. Talks about strings and seq() which, as shown above, is not equivalent to range().

As far as I can tell `seq` simply *never* generates an empty sequence, except when invoked on an empty vector. — Konrad Rudolph, Feb 14 '22 at 11:59
See `?sequence`. For example `sequence(from = 1, 3)`; `sequence(from = 1, 0)` — alexis_laz, Feb 14 '22 at 12:44

caldwellst · Accepted Answer · 2022-02-14T12:11:54.657

There is no exact equivalent. As noted, seq doesn't work because the by argument is automatically set with the correct sign, and generates an error if you try to explicitly pass a positive sign when to < from. Just create a very simple wrapper if you need to have the exact match.

py_range <- function(from, to) {
  if (to <= from) return(integer(0))
  seq(from = from, to = to - 1)
}

py_range(1, 4)
#> [1] 1 2 3
py_range(1, 0)
#> integer(0)
py_range(1, 1)
#> integer(0)

These will work in a loop with printing as you desire.

for (i in py_range(1, 4)) {
  print(i)
}
#> [1] 1
#> [1] 2
#> [1] 3

for (i in py_range(1, 0)) {
  print(i)
}
#> Nothing was actually printed here!

for (i in py_range(1, 1)) {
  print(i)
}
#> Nothing was actually printed here!

score 0 · Answer 2 · edited Feb 14 '22 at 13:30

0

seq works well in this case:

> x <- NULL
> for (i in seq(x)) print(i)
> #

Thanks

edited Feb 14 '22 at 13:30

Dharman

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answered Feb 14 '22 at 13:24

Janvier NTWALI

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R equivalent of Python's range() function

2 Answers2