Ranges-class {IRanges} | R Documentation

## Ranges objects

### Description

The Ranges virtual class is a general container for storing a set of integer ranges.

### Details

A Ranges object is a vector-like object where each element describes a "range of integer values".

A "range of integer values" is a finite set of consecutive integer values. Each range can be fully described with exactly 2 integer values which can be arbitrarily picked up among the 3 following values: its "start" i.e. its smallest (or first, or leftmost) value; its "end" i.e. its greatest (or last, or rightmost) value; and its "width" i.e. the number of integer values in the range. For example the set of integer values that are greater than or equal to -20 and less than or equal to 400 is the range that starts at -20 and has a width of 421. In other words, a range is a closed, one-dimensional interval with integer end points and on the domain of integers.

The starting point (or "start") of a range can be any integer (see `start` below) but its "width" must be a non-negative integer (see `width` below). The ending point (or "end") of a range is equal to its "start" plus its "width" minus one (see `end` below). An "empty" range is a range that contains no value i.e. a range that has a null width. Note that for an empty range, the end is smaller than the start.

The length of a Ranges object is the number of ranges in it, not the number of integer values in its ranges.

A Ranges object is considered empty iff all its ranges are empty.

Ranges objects have a vector-like semantic i.e. they only support single subscript subsetting (unlike, for example, standard R data frames which can be subsetted by row and by column).

The Ranges class itself is a virtual class. The following classes derive directly from the Ranges class: IRanges and XRanges.

### Methods

In the code snippets below, `x`, `y` and `object` are Ranges objects. Not all the functions described below will necessarily work with all kinds of Ranges objects but they should work at least for IRanges objects. Also more operations on Ranges objects are described in the man page for IRanges-utils (`shift`, `restrict`, `narrow`, `reduce`, `gaps`), for IntervalTree objects (`overlap`) and for RangesList objects (`split` method for Ranges objects).

  `length(x)`: The number of ranges in `x`.
  `start(x)`: The start values of the ranges. This is an integer vector of the same length as `x`.
  `width(x)`: The number of integer values in each range. This is a vector of non-negative integers of the same length as `x`.
  `end(x)`: `start(x) + width(x) - 1L`
  `mid(x)`: returns the midpoint of the range, `start(x) + floor((width(x) - 1)/2)`.
  `names(x)`: `NULL` or a character vector of the same length as `x`.
  `update(object, ...)`: Convenience method for combining multiple modifications of `object` in one single call. For example `object <- update(object, start=start(object)-2L, end=end(object)+2L)` is equivalent to `start(object) <- start(object)-2L; end(object) <- end(object)+2L`.
  `isEmpty(x)`: Return a logical value indicating whether `x` is empty or not.
  `isDisjoint(x)`: Return a logical value indicating whether the ranges `x` are disjoint (i.e. non-overlapping).
  `as.matrix(x, ...)`: Convert `x` into a 2-column integer matrix containing `start(x)` and `width(x)`. Extra arguments (`...`) are ignored.
  `as.data.frame(x, row.names=NULL, optional=FALSE, ...)`: Convert `x` into a standard R data frame object. `row.names` must be `NULL` or a character vector giving the row names for the data frame, and `optional` and any additional argument (`...`) is ignored. See `?as.data.frame` for more information about these arguments.
  `as.integer(x)`: Convert `x` into an integer vector, by converting each range into the integer sequence formed by `from:to` and concatenating them together.
  `x[i]`: Return a new Ranges object (of the same type as `x`) made of the selected ranges. `i` can be a numeric vector, a logical vector, `NULL` or missing. If `x` is a NormalIRanges object and `i` a positive numeric subscript (i.e. a numeric vector of positive values), then `i` must be strictly increasing.
  `rep(x, times)`: Return a new Ranges object made of the repeated elements.
  `c(x, ...)`: Combine `x` and the Ranges objects in `...` together. Any object in `...` must belong to the same class as `x`, or to one of its subclasses, or must be `NULL`. The result is an object of the same class as `x`. NOTE: Only works for IRanges (and derived) objects for now.
  `x * y`: The arithmetic operation `x * y` is for centered zooming. It symmetrically scales the width of `x` by `1/y`, where `y` is a numeric vector that is recycled as necessary. For example, `x * 2` results in ranges with half their previous width but with approximately the same midpoint. The ranges have been “zoomed in”. If `y` is negative, it is equivalent to `x * (1/abs(y))`. Thus, `x * -2` would double the widths in `x`. In other words, `x` has been “zoomed out”.

### Normality

A Ranges object `x` is implicitly representing an arbitrary finite set of integers (that are not necessarily consecutive). This set is the set obtained by taking the union of all the values in all the ranges in `x`. This representation is clearly not unique: many different Ranges objects can be used to represent the same set of integers. However one and only one of them is guaranteed to be "normal".

By definition a Ranges object is said to be "normal" when its ranges are: (a) not empty (i.e. they have a non-null width); (b) not overlapping; (c) ordered from left to right; (d) not even adjacent (i.e. there must be a non empty gap between 2 consecutive ranges).

Here is a simple algorithm to determine whether `x` is "normal": (1) if `length(x) == 0`, then `x` is normal; (2) if `length(x) == 1`, then `x` is normal iff `width(x) >= 1`; (3) if `length(x) >= 2`, then `x` is normal iff:

      start(x)[i] <= end(x)[i] < start(x)[i+1] <= end(x)[i+1]

for every 1 <= `i` < `length(x)`.

The obvious advantage of using a "normal" Ranges object to represent a given finite set of integers is that it is the smallest in terms of of number of ranges and therefore in terms of storage space. Also the fact that we impose its ranges to be ordered from left to right makes it unique for this representation.

A special container (NormalIRanges) is provided for holding a "normal" IRanges object: a NormalIRanges object is just an IRanges object that is guaranteed to be "normal".

Here are some methods related to the notion of "normal" Ranges:

  `isNormal(x)`: Return a logical value indicating whether `x` is "normal" or not.
  `whichFirstNotNormal(x)`: Return `NA` if `x` is normal, or the smallest valid indice `i` in `x` for which `x[1:i]` is not "normal".

### Author(s)

H. Pages and M. Lawrence

### See Also

Ranges-comparison, IRanges-class, IRanges-utils, IRanges-setops, XRanges-class, RangedData-class, IntervalTree-class, `update`, `as.matrix`, `as.data.frame`, `rep`

### Examples

      x <- IRanges(start=c(2:-1, 13:15), width=c(0:3, 2:0))
      x
      length(x)
      start(x)
      width(x)
      end(x)
      isEmpty(x)
      as.matrix(x)
      as.data.frame(x)

      ## Subsetting:
      x[4:2]                  # 3 ranges
      x[-1]                   # 6 ranges
      x[FALSE]                # 0 range
      x0 <- x[width(x) == 0]  # 2 ranges
      isEmpty(x0)

      ## Use the replacement methods to resize the ranges:
      width(x) <- width(x) * 2 + 1
      x
      end(x) <- start(x)            # equivalent to width(x) <- 0
      x
      width(x) <- c(2, 0, 4)
      x
      start(x)[3] <- end(x)[3] - 2  # resize the 3rd range
      x

      ## Name the elements:
      names(x)
      names(x) <- c("range1", "range2")
      x
      x[is.na(names(x))]  # 5 ranges
      x[!is.na(names(x))]  # 2 ranges

      ## Check for disjointedness
      isDisjoint(IRanges(c(2,5,1), c(3,7,3))) ## FALSE
      isDisjoint(IRanges(c(2,9,5), c(3,9,6))) ## TRUE
      isDisjoint(IRanges(1, 5)) ## TRUE

      ir <- IRanges(c(1,5), c(3,10))
      ir*1 # no change
      ir*c(1,2) # zoom second range by 2X
      ir*-2 # zoom out 2X

[Package IRanges version 1.2.3 Index]