GTuples-class {GenomicTuples} | R Documentation

## GTuples objects

### Description

The `GTuples` class is a container for the genomic tuples and their associated annotations.

### Details

`GTuples` extends `GRanges` as a container for genomic tuples rather than genomic ranges. `GTuples` is a vector of genomic locations and associated annotations. Each element in the vector is comprised of a sequence name, a tuple, a `strand`, and optional metadata columns (e.g. score, GC content, etc.). This information is stored in four components:

`seqnames`

  a 'factor' `Rle` object containing the sequence names.

`tuples`

  externally, a matrix-link object containing the tuples. Internally, an `IRanges` object storing the first and last position of each tuple and, if required, a matrix storing the "internal" positions of each tuple (see description of `internalPos` below).

`strand`

  a `Rle` Rle object containing the strand information.

`mcols`

  a `DataFrame` object containing the metadata columns. Columns cannot be named "`seqnames`" "`ranges`", "`tuples`", "`internalPos`", "`size`", "`strand`", "`seqlevels`", "`seqlengths`", "`isCircular`", "`start`", "`end`", "`width`", or "`element`".

`seqinfo`

  a `DataFrame` object containing information about the set of genomic sequences present in the `GTuples` object.

### Slots

Since the `GTuples` class extends the `GRanges` class it contains the `seqnames`, `ranges`, `strand`, `elementMetadata`, `seqinfo` and `metadata`. The `GTuples` class also contains two additional slots, `size` and `internalPos`.

`size`

  An integer. The `size` of the genomic tuples stored in the `GTuples` object.

`internalPos`

  If the `size` of the genomic tuples is greater than 2, `internalPos` is an integer `matrix` storing the "internal" positions of each genomic tuple. Otherwise `internalPos` is `NULL`.

### Constructor

  `GTuples(seqnames = Rle(), tuples = matrix(), strand = Rle("*", length(seqnames)), ..., seqlengths = NULL, seqinfo = NULL)`: Creates a `GTuples` object.

  `seqnames`

    `Rle` object, character vector, or factor containing the sequence names.

  `tuples`

    matrix object containing the positions of the tuples. The first column should refer to pos1, the second to pos2, etc.

  `strand`

    `Rle` object, character vector, or factor containing the strand information.

  `...`

    Optional metadata columns. These columns cannot be named "`start`", "`end`", "`width`", or "`element`". A named integer vector "`seqlength`" can be used instead of `seqinfo`.

  `seqlengths`

    an integer vector named with the sequence names and containing the lengths (or `NA`) for each `level(seqnames)`.

  `seqinfo`

    a `DataFrame` object containing allowed sequence names and lengths (or `NA`) for each `level(seqnames)`.

### Coercion

In the code snippets below, `x` is a GTuples object.

  `as.data.frame(x, row.names = NULL, optional = FALSE, ...)`: Creates a data.frame with columns `seqnames` (factor), `tuples` (integer), `strand` (factor), as well as the additional metadata columns stored in `mcols(x)`. Pass an explicit `stringsAsFactors=TRUE/FALSE` argument via `...` to override the default conversions for the metadata columns in `mcols(x)`.

  `as.character(x, ignore.strand=FALSE)`: Turn GTuples object `x` into a character vector where each tuples in `x` is represented by a string in format `chr1:100,109,115:+`. If `ignore.strand` is TRUE or if all the ranges in `x` are unstranded (i.e. their strand is set to `*`), then all the strings in the output are in format `chr1:100,109,115`.

  The names on `x` are propagated to the returned character vector. Its metadata (`metadata(x)`) and metadata columns (`mcols(x)`) are ignored.

  `as.factor(x)`: Equivalent to

        factor(as.character(x), levels=as.character(sort(unique(x))))

  `as(x, "GRanges"), granges(x)`: Creates a `GRanges` object from a `GTuples` object. WARNING: This is generally a destructive operation because all "internal" positions will be dropped.

### Accessors

In the following code snippets, x is a `GTuples` object.

  `size(x)`: Get the size of the genomic tuples stored in `x`.

  `length(x)`: Get the number of elements.

  `seqnames(x)`, `seqnames(x) <- value`: Get or set the sequence names. `value` can be an `Rle` object, a character vector, or a factor.

  `tuples(x)`, `tuples(x) <- value`: Get the positions of the tuples, which are returned as an integer matrix. `value` can be an integer matrix.

  `ranges(x, use.mcols = FALSE)`, `ranges(x) <- value`: Get or set the ranges in the form of a CompressedIRangesList. `value` can be a IntegerRangesList object.

  WARNING: The use of `ranges` with `GTuples` objects is strongly discouraged. It will only get/set pos_{1} and pos_{m} of the tuples, where m is the `size` of the tuples, as these are what are stored in the "ranges" slot of a `GTuples` object.

  `names(x)`, `names(x) <- value`: Get or set the names of the elements.

  `strand(x)`, `strand(x) <- value`: Get or set the strand. `value` can be an `Rle` object, character vector, or factor.

  `mcols(x, use.names=FALSE)`, `mcols(x) <- value`: Get or set the metadata columns. If `use.names=TRUE` and the metadata columns are not `NULL`, then the names of `x` are propagated as the row names of the returned `DataFrame` object. When setting the metadata columns, the supplied value must be `NULL` or a data.frame-like object (i.e. `DataTable` or `data.frame`) object holding element-wise metadata.

  `elementMetadata(x)`, `elementMetadata(x) <- value`, `values(x)`, `values(x) <- value`: Alternatives to `mcols` functions. Their use is discouraged.

  `seqinfo(x)`, `seqinfo(x) <- value`: Get or set the information about the underlying sequences. `value` must be a `DataFrame` object.

  `seqlevels(x)`, `seqlevels(x, force=FALSE) <- value`: Get or set the sequence levels. `seqlevels(x)` is equivalent to `seqlevels(seqinfo(x))` or to `levels(seqnames(x))`, those 2 expressions being guaranteed to return identical character vectors on a `GTuples` object. `value` must be a character vector with no `NA`s. See `?``seqlevels` for more information.

  `seqlengths(x)`, `seqlengths(x) <- value`: Get or set the sequence lengths. `seqlengths(x)` is equivalent to `seqlengths(seqinfo(x))`. `value` can be a named non-negative integer or numeric vector eventually with `NA`s.

  `isCircular(x)`, `isCircular(x) <- value`: Get or set the circularity flags. `isCircular(x)` is equivalent to `isCircular(seqinfo(x))`. `value` must be a named logical vector eventually with `NA`s.

  `genome(x)`, `genome(x) <- value`: Get or set the genome identifier or assembly name for each sequence. `genome(x)` is equivalent to `genome(seqinfo(x))`. `value` must be a named character vector eventually with `NA`s.

  `seqlevelsStyle(x)`, `seqlevelsStyle(x) <- value`: Get or set the seqname style for `x`. See the `seqlevelsStyle` generic getter and setter in the GenomeInfoDb package for more information.

  `score(x)`, `score(x) <- value`: Get or set the "score" column from the element metadata.

### Tuples methods

In the following code snippets, x is a `GTuples` object. WARNING: The preferred setter is `tuples(x) <- value` and the use of `start(x) <- value`, `end(x) <- value` and `width(x) <- value is discouraged`.

  `start(x)`, `start(x) <- value`: Get or set pos_{1} of the tuples. WARNING: The use of `width(x) <- value` is discouraged; instead, construct the tuples as the appropriate integer matrix, `mvalue`, and use `tuples(x) <- mvalue`.

  `end(x)`, `end(x) <- value`: Get or set pos_{m} of the tuples, where m is the `size` of the tuples. WARNING: The use of `end(x) <- value` is discouraged; instead, construct the tuples as the appropriate integer matrix, `mvalue`, and use `tuples(x) <- mvalue`.

  `IPD(x)`: Get the intra-pair distances (`IPD`). `IPD` is only defined for tuples with `size` > 1. The `IPD` of a tuple with `size`= m is the vector of intra-pair distances, (pos_{2} - pos_{1}, …, pos_{m} - pos_{m - 1}).

  `width(x)`, `width(x) <- value`: Get or set pos_{m} - pos_{1} of the tuples, where m is the `size` of the tuples. If using `width(x) <- value`, pos_{1} is held fixed and pos_{m} is altered. WARNING: The use of `width(x) <- value` is discouraged; instead, construct the tuples as the appropriate integer matrix, `mvalue`, and use `tuples(x) <- mvalue`.

### Splitting and Combining

In the following code snippets, x is a `GTuples` object.

  `append(x, values, after = length(x))`: Inserts the values into `x` at the position given by after, where `x` and `values` are of the same class.

  `c(x, ...)`: Combines `x` and the `GTuples` 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`.

  `c(x, ..., ignore.mcols=FALSE)` If the `GTuples` objects have metadata columns (represented as one `DataFrame` per object), each such `DataFrame` must have the same columns in order to combine successfully. In order to circumvent this restraint, you can pass in an `ignore.mcols=TRUE` argument which will combine all the objects into one and drop all of their metadata columns.

  `split(x, f, drop=FALSE)`: Splits `x` according to `f` to create a `GTuplesList` object. If `f` is a list-like object then `drop` is ignored and `f` is treated as if it was `rep(seq_len(length(f)), sapply(f, length))`, so the returned object has the same shape as `f` (it also receives the names of `f`). Otherwise, if `f` is not a list-like object, empty list elements are removed from the returned object if `drop` is `TRUE`.

### Subsetting

In the following code snippets, x is a `GTuples` object.

  `x[i, j]`, `x[i, j] <- value`: Get or set elements `i` with optional metadata columns `mcols(x)[,j]`, where `i` can be missing; an `NA`-free logical, numeric, or character vector; or a 'logical' `Rle` object.

  `x[i,j] <- value`: Replaces elements `i` and optional metadata columns `j` with `value`.

  `head(x, n = 6L)`: If `n` is non-negative, returns the first `n` elements of the `GTuples` object. If `n` is negative, returns all but the last `abs(n)` elements of the `GTuples` object.

  `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 whole vector 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.

  `subset(x, subset)`: Returns a new object of the same class as `x` made of the subset using logical vector subset, where missing values are taken as `FALSE`.

  `tail(x, n = 6L)`: If `n` is non-negative, returns the last `n` elements of the `GTuples` object. If `n` is negative, returns all but the first `abs(n)` elements of the `GTuples` object.

  `window(x, start = NA, end = NA, width = NA, frequency = NULL, delta = NULL, ...)`: Extracts the subsequence window from the `GTuples` object using:

  `start`, `end`, `width`

    The start, end, or width of the window. Two of the three are required.

  `frequency`, `delta`

    Optional arguments that specify the sampling frequency and increment within the window.

  In general, this is more efficient than using `"["` operator.

  `window(x, start = NA, end = NA, width = NA, keepLength = TRUE) <- value`: Replaces the subsequence window specified on the left (i.e. the subsequence in `x` specified by `start`, `end` and `width`) by `value`. `value` must either be of class `class(x)`, belong to a subclass of `class(x)`, be coercible to `class(x)`, or be `NULL`. If `keepLength` is `TRUE`, the elements of `value` are repeated to create a `GTuples` object with the same number of elements as the width of the subsequence window it is replacing. If `keepLength` is `FALSE`, this replacement method can modify the length of `x`, depending on how the length of the left subsequence window compares to the length of `value`.

  `x$name`, `x$name <- value`: Shortcuts for `mcols(x)$name` and `mcols(x)$name <- value`, respectively. Provided as a convenience, from `GRanges` as the result of strong popular demand. Note that those methods are not consistent with the other `$` and `$<-` methods in the `IRanges`/ `GenomicRanges` infrastructure, and might confuse some users by making them believe that a `GRanges` object can be manipulated as a data.frame-like object. Therefore we recommend using them only interactively, and we discourage their use in scripts or packages. For the latter, use `mcols(x)$name` and `mcols(x)$name <- value`, instead of `x$name` and `x$name <- value`, respectively.

### Other methods

item `show(x)`: By default the show method displays 5 head and 5 tail elements. This can be changed by setting the global options `showHeadLines` and `showTailLines`. If the object length is less than (or equal to) the sum of these 2 options plus 1, then the full object is displayed. Note that these options also affect the display of `GRanges`, `GAlignments` and `GAlignmentPairs` objects (defined in the GenomicAlignments package), as well as other objects defined in the IRanges and Biostrings packages (e.g. `IRanges` and `DNAStringSet` objects).

### Author(s)

Peter Hickey

### See Also

`GTuplesList-class`, `seqinfo`, `Vector-class`, `Rle-class`, `DataFrame`, `GRanges-class`, `intra-tuple-methods`, `findOverlaps-methods`, `nearest-methods`,

### Examples

      ## Create example 4-tuples
      seqinfo <- Seqinfo(paste0("chr", 1:3), c(1000, 2000, 1500), NA, "mock1")
      gt4 <- GTuples(seqnames = Rle(c("chr1", "chr2", "chr1", "chr3"),
                                    c(1, 3, 2, 4)),
                     tuples = matrix(c(1:10, 2:11, 3:12, 4:13), ncol = 4),
                     strand = Rle(strand(c("-", "+", "*", "+", "-")),
                                  c(1, 2, 2, 3, 2)),
                     score = 1:10, GC = seq(1, 0, length = 10), seqinfo = seqinfo)
      gt4

      ## Summarizing elements
      table(seqnames(gt4))
      sum(width(gt4))
      summary(mcols(gt4)[,"score"])

      ## Renaming the underlying sequences
      seqlevels(gt4)
      seqlevels(gt4) <- sub("chr", "Chrom", seqlevels(gt4))
      gt4
      seqlevels(gt4) <- sub("Chrom", "chr", seqlevels(gt4)) # revert

      ## Combining objects
      gt4_a <- GTuples(seqnames = Rle(c("chr1", "chr2", "chr1", "chr3"),
                                    c(1, 3, 2, 4)),
                     tuples = matrix(c(1:10, 21:30, 31:40, 41:50), ncol = 4),
                     strand = Rle(strand(c("-", "+", "*", "+", "-")),
                                  c(1, 2, 2, 3, 2)),
                     score = 1:10, seqinfo = seqinfo)

      gt4_b <- GTuples(seqnames = Rle(c("chr1", "chr2", "chr1", "chr3"),
                                    c(1, 3, 2, 4)),
                     tuples = matrix(c(101:110, 121:130, 131:140, 141:150),
                                     ncol = 4),
                     strand = Rle(strand(c("-", "+", "*", "+", "-")),
                                  c(1, 2, 2, 3, 2)),
                     score = 1:10, seqinfo = seqinfo)

      some_gt4 <- c(gt4_a, gt4_b)

      ## all_gt4 <- c(gt4, gt4_a, gt4_b) ## (This would fail)
      all_gt4 <- c(gt4, gt4_a, gt4_b, ignore.mcols=TRUE)

      ## The number of lines displayed in the 'show' method
      ## are controlled with two global options.
      options("showHeadLines" = 7)
      options("showTailLines" = 2)
      all_gt4

      ## Revert to default values
      options("showHeadLines"=NULL)
      options("showTailLines"=NULL)

      ## Get the size of the tuples stored in the GTuples object
      size(gt4)

      ## Get the tuples
      tuples(gt4)

      ## Get the matrix of intra-pair distances (IPD)
      IPD(all_gt4)

      ## Can't combine genomic tuples of different sizes
      gt1 <- GTuples('chr1', matrix(30:40))
      gt1
      ## Not run:
      ## Returns error
      c(gt4, gt1)

    ## End(Not run)

[Package GenomicTuples version 1.18.1 Index]