sequences: Utilities for creating many sequences

In cheapr: Simple Functions to Save Time and Memory

Utilities for creating many sequences

Description

seq_ is a vectorised version of seq with some additional features.
seq_size returns sequence sizes.
seq_start returns sequence start points.
seq_end returns sequence end points.
seq_increment returns sequence increments.
sequence_ is an extension to sequence which accepts decimal number increments.
seq_id can be paired with sequence_ to group individual sequences.
window_sequence creates a vector of window sizes for rolling calculations.
lag_sequence creates a vector of lags for rolling calculations.
lead_sequence creates a vector of leads for rolling calculations.

Usage

sequence_(size, from = 1L, by = 1L, add_id = FALSE, as_list = FALSE)

seq_id(size)

seq_(
  from = NULL,
  to = NULL,
  by = NULL,
  size = NULL,
  add_id = FALSE,
  as_list = FALSE
)

seq_size(from, to, by = 1L)

seq_start(size, to, by = 1L)

seq_end(size, from, by = 1L)

seq_increment(size, from, to)

window_sequence(size, k, partial = TRUE, ascending = TRUE, add_id = FALSE)

lag_sequence(size, k, partial = TRUE, add_id = FALSE)

lead_sequence(size, k, partial = TRUE, add_id = FALSE)

Arguments

size	Vector of sequence lengths.
from	Start of sequence(s).
by	Unit increment of sequence(s).
add_id	Should the ID numbers of the sequences be added as names? Default is FALSE.
as_list	Should a list of sequences be returned? Setting to TRUE would place each distinct sequence vector into a distinct list element. The default is FALSE.
to	End of sequence(s).
k	Window/lag size.
partial	Should partial windows/lags be returned? Default is TRUE.
ascending	Should window sequence be ascending? Default is TRUE.

Details

seq_() is a fast vectorised version of seq() with powerful features. It can return many sequences as a single vector of combined sequences or a list of sequences.

sequence_() works in the same way as sequence() but can accept non-integer by values. This is the workhorse function of seq_().

Unlike sequence(), sequence_() recycles all its arguments, including size.

If any of the sequences contain values > .Machine$integer.max, then the result will always be a double vector.

Value

A vector of length sum(size) except for seq_ which returns a vector of size sum((to - from) / (by + 1))

Examples

library(cheapr)

# These two functions are similar
sequence(1:3);sequence_(1:3)

# sequence_() can handle any numeric vector sequence
sequence(1:3, by = 0.1);sequence_(1:3, by = 0.1)

# Alternatively return as a list of sequences

sequence_(1:3, by = 0.1, as_list = TRUE)

# Add IDs to the sequences
sequence_(1:3, by = 0.1, add_id = TRUE)
# Turn this quickly into a data frame
seqs <- sequence_(1:3, by = 0.1, add_id = TRUE)
new_df(name = names(seqs), seq = seqs)

sequence(c(3, 2), by = c(-0.1, 0.1));sequence_(c(3, 2), by = c(-0.1, 0.1))

# Vectorised version of seq()
seq_(1, 10, by = c(1, 0.5))
# Same as above
c(seq(1, 10, 1), seq(1, 10, 0.5))

# Again, as a list of sequences
# 2 different start points and 2 different increments
seq_(from = c(-1, 1), 3, by = c(1, 0.5), as_list = TRUE)

# Programmers may use seq_size() to determine final sequence lengths

sizes <- seq_size(1, 10, by = c(1, 0.5))
print(paste(c("sequence sizes: (", sizes, ") total size:", sum(sizes)),
            collapse = " "))

# Or return as a list of sequences
# Note that these lengths will match the above line of code
seq_(1, 10, by = c(1, 0.5), as_list = TRUE) |>
  list_lengths()

# Sequences of dates with different increments

from <- Sys.Date()
to <- from + 10
by <- c(1, 2, 3)
date_seqs <- seq_(from, to, by, as_list = TRUE)
lapply(date_seqs, function(x) `class<-`(x, "Date"))

# Utilities for rolling calculations

# A window sequence of size 3 for a vector of size 10
# This tells us how big the window should be when looking backwards
window_sequence(10, 3, partial = FALSE)
window_sequence(10, 3, partial = TRUE)

window_sequence(c(3, 5), 3)
window_sequence(c(3, 5), 3, partial = FALSE)
window_sequence(c(3, 5), 3, partial = TRUE, ascending = FALSE)

# Lag sequence of size 3 for a vector of size 10
# This tells us how for we should look backwards at any given point
lag_sequence(10, 3, partial = FALSE)
# How far to look forwards
lead_sequence(10, 3, partial = FALSE)

lag_sequence(10, 3, partial = TRUE)
lead_sequence(10, 3, partial = TRUE)
# One can for example use these in data.table::frollsum

cheapr documentation built on Nov. 28, 2025, 5:06 p.m.