segment: Segment a sequence into shifted versions of itself

Description

Create a shifted version of a sequence to make it easier to do certain types of analysis.

Arguments

A vector

do.pad

Whether the vector should be padded to contain the edges of the sequence

Value

The return value is a data.frame with dimensions length(x) - 1 by 2 or length(x) + 1 by 2 if do.pad == TRUE. A data.frame is used to support arbitrary types. For example, using a Date vector will result in a numeric output, which is inconvenient.

Usage

segment(x, do.pad=FALSE)

Details

Segmenting sequences into offset versions of itself is useful for detecting patterns in sequences. This approach is compatible with a functional programming style as each row can then be passed to a map-vectorized function for further processing. The advantage over an iterative approach is that the map-vectorized function can focus on a row-specific model independent of data management mechanics like maintaining proper indices while iterating over the sequence, as this is handled by segment.

Examples

Run this code

segment(1:10)

# Notice how the ends of the sequence are given their own rows
segment(1:10, TRUE)

# Emulate segment using partition
partition(1:10, function(x) x, 1)

# Emulate segment using maprange
t(maprange(1:10, 2, function(x) x))

# Create four shifted copies instead of two
maprange(1:10, 4, function(x) x)