IPosRanges-class: IPosRanges objects
In Bioconductor/IRanges: Foundation of integer range manipulation in Bioconductor

IPosRanges-class

R Documentation

IPosRanges objects

Description

The IPosRanges virtual class is a general container for storing a vector of ranges of integer positions.

Details

An IPosRanges object is a vector-like object where each element describes a "range of integer positions".

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. Depending on the context, it can be interpreted either as just the empty set of integers or, more precisely, as the position between its "end" and its "start" (note that for an empty range, the "end" equals the "start" minus one).

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

An IPosRanges object is considered empty iff all its ranges are empty.

IPosRanges 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 IPosRanges class itself is a virtual class. The following classes derive directly from it: IRanges, IPos, NCList, and GroupingRanges.

Methods

In the code snippets below, x, y and object are IPosRanges objects. Not all the functions described below will necessarily work with all kinds of IPosRanges derivatives but they should work at least for IRanges objects.

Note that many more operations on IPosRanges objects are described in other man pages of the IRanges package. See for example the man page for intra range transformations (e.g. shift(), see ?`intra-range-methods`), or the man page for inter range transformations (e.g. reduce(), see ?`inter-range-methods`), or the man page for findOverlaps methods (see ?`findOverlaps-methods`), or the man page for IntegerRangesList objects where the split method for IntegerRanges derivatives is documented.

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.

tile(x, n, width, ...):

Splits each range in x into subranges as specified by n (number of ranges) or width. Only one of n or width can be specified. The return value is a IRangesList the same length as x. IPosRanges with a width less than the width argument are returned unchanged.

slidingWindows(x, width, step=1L):

Generates sliding windows within each range of x, of width width, and starting every step positions. The return value is a IRangesList the same length as x. IPosRanges with a width less than the width argument are returned unchanged. If the sliding windows do not exactly cover x, the last window is partial.

isEmpty(x):

Return a logical value indicating whether x is empty or not.

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 is ignored. See ?as.data.frame for more information about these arguments.

x[[i]]:

Return integer vector start(x[i]):end(x[i]) denoted by i. Subscript i can be a single integer or a character string.

x[i]:

Return a new IPosRanges 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, length.out, each):

Repeats the values in x through one of the following conventions:

times: Vector giving the number of times to repeat each element if of length length(x), or to repeat the IPosRanges elements if of length 1.
length.out: Non-negative integer. The desired length of the output vector.
each: Non-negative integer. Each element of x is repeated each times.

c(x, ..., ignore.mcols=FALSE):

Concatenate IPosRanges object x and the IPosRanges objects in ... together. See ?c in the S4Vectors package for more information about concatenating Vector derivatives.

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”.

x + y:

Expands the ranges in x on either side by the corresponding value in the numeric vector y.

show(x):

By default the show method displays 5 head and 5 tail lines. The number of lines can be altered by setting the global options showHeadLines and showTailLines. If the object length is less than the sum of the options, the full object is displayed. These options affect display of IRanges, IPos, Hits, GRanges, GPos, GAlignments, XStringSet objects, and more...

Normality

An IPosRanges 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 IPosRanges 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 an IPosRanges 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 IPosRanges object to represent a given finite set of integers is that it is the smallest in terms 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 IPosRanges:

isNormal(x):: Return TRUE or FALSE 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. Pagès and M. Lawrence

Examples

## ---------------------------------------------------------------------
## Basic manipulation
## ---------------------------------------------------------------------
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

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

Bioconductor/IRanges documentation built on Nov. 17, 2024, 6:54 p.m.