seq()

seq(from = 1, to = 1, by = ((to - from)/(length.out - 1)), length.out = NULL, along.with = NULL)

seq() creates sequences of numbers with precise control over start, end, length, and step size. It’s essential for looping, creating index vectors, and generating test data.

Syntax

seq(from = 1, to = 1, by = ((to - from)/(length.out - 1)), length.out = NULL, along.with = NULL)

Parameters

Parameter	Type	Default	Description
from	numeric	1	Starting value of the sequence
to	numeric	1	Ending value (inclusive)
by	numeric	(to-from)/(length.out-1)	Step size (increment)
length.out	integer	NULL	Desired length of the sequence
along.with	vector	NULL	Take length from this object

Examples

Basic sequence from 1 to 10

seq(1, 10)
#  [1]  1  2  3  4  5  6  7  8  9 10

Sequence with custom increment

seq(0, 100, by = 10)
#  [1]   0  10  20  30  40  50  60  70  80  90 100

seq(1, 9, by = 2)
# [1] 1 3 5 7 9

Sequence with specified length

seq(0, 1, length.out = 5)
# [1] 0.00 0.25 0.50 0.75 1.00

seq(0, 10, length.out = 3)
# [1]  0  5 10

Using along.with to match another vector’s length

x <- c("a", "b", "c", "d")
seq(along.with = x)
# [1] 1 2 3 4

seq(10, 50, along.with = x)
# [1] 10 23 36 50

Negative sequences

seq(10, 1, by = -1)
#  [1] 10  9  8  7  6  5  4  3  2  1

seq(5, -5, length.out = 11)
#  [1]  5  4  3  2  1  0 -1 -2 -3 -4 -5

Fractional sequences

seq(0, 1, by = 0.1)
#  [1] 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Common Patterns

Creating index vectors for loops

n <- 5
for (i in seq_len(n)) {
  print(i)
}
# [1] 1
# [1] 2
# [1] 3
# [1] 4
# [1] 5

Generating test data frames

df <- data.frame(
  id = seq(1, 100),
  value = seq(0, 99) ^ 2
)
head(df)
#   id value
# 1  1     0
# 2  2     1
# 3  3     4
# 4  4     9
# 5  5    16
# 6  6    25

Creating time-based sequences

# Daily sequence for a week
seq(as.Date("2026-01-01"), as.Date("2026-01-07"), by = "day")
# [1] "2026-01-01" "2026-01-02" "2026-01-03" "2026-01-04" "2026-01-05"
# [6] "2026-01-06" "2026-01-07"

Reproducible sequences with set.seed

set.seed(42)
seq_len(5) + sample(0:10, 5)
# [1]  3  8 12  7 11

See Also

• c()
• rep()
• sample()