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Subset a numeric series by position

Source: R/subset_discretes.R
subset_discretes.Rd

When a series has a well-defined "first" element (e.g. natural1() starts at 1), subsetting with [] materializes a specified part of the series, and mirrors the behaviour of numeric vector subsetting. Positive i returns the discrete values at those positions, and negative i tries to return the full series with the specified positions dropped.

Usage

# S3 method for class 'discretes'
x[i]

# S3 method for class 'discretes'
x[i] <- value

Arguments

x

A numeric series (object of class "discretes").

i

Numeric vector of indices. Omit for the full series (finite only).

value

Replacement value; ignored, because replacement via [<- is not supported.

Value

A vector of discrete values. When the series has no first element or too few values for positive i, R returns NA as for ordinary vectors. For negative i or missing i, the full series is obtained first; infinite series behaviour defaults to that of get_discretes_in().

Details

Subsetting via [] tries to delegate to native behaviour on numeric vectors as quickly as possible by first materializing the series as a vector, and then conducting the subsetting.

  • If i is missing or has negative values, subsetting is delegated to the full series materialized via get_discretes_in() (if possible).

  • If i is NULL or length-0, subsetting is delegated to a representative value of the series.

  • If i doesn't have negative values, subsetting is delegated to the series materialized as far out as needed to cover all is, via next_discrete() from -Inf.

Note

Unlike subsetting numeric vectors, the following actions are not supported:

  • Replacement via [<- (throws an error).

  • Subsetting by a character vector, as though subsetting by entry names.

  • Subsetting by a logical vector.

Examples

natural1()[2]
#> [1] 2
natural1()[c(1, 3, 5)]
#> [1] 1 3 5
integers(1, 5)[-1]   # full series with first value dropped
#> [1] 2 3 4 5

# Subsetting from the other side of a sink
x <- 1 / natural1()
x[1:3]   # No such thing as a "first" value; returns NA.
#> [1] NA NA NA
y <- dsct_union(x, -1)
y[1:3]   # "-1" is the 1st value, but no such thing as 2nd or 3rd value.
#> [1] -1 NA NA