group_by {RGMQL} | R Documentation

## Method group_by

### Description

Wrapper to GMQL GROUP operator

It performs the grouping of samples and/or sample regions of the input dataset based on one specified metadata and/or region attribute. If the metadata attribute is multi-value, i.e., it assumes multiple values for sample (e.g., both <disease, cancer> and <disease, diabetes>), the grouping identifies different groups of samples for each attribute value combination (e.g., group1 for samples that feature the combination <disease, cancer>, group2 for samples that feature the combination <disease, diabetes>, and group3 for samples that feature both combinations <disease, cancer> and <disease, diabetes>). For each obtained group, it is possible to request the evaluation of aggregate functions on metadata attributes; these functions consider the metadata contained in all samples of the group. The regions, their attributes and their values in output are the same as the ones in input for each sample, and the total number of samples does not change. All metadata in the input samples are conserved with their values in the output samples, with the addition of the "_group" attribute, whose value is the identifier of the group to which the specific sample is assigned; other metadata attributes can be added as aggregate functions computed on specified metadata. When used on region attributes, group_by can group regions of each sample individually, based on their coordinates (chr, start, stop, strand) and possibly also on other specified grouping region attributes (when these are present in the schema of the input dataset). In each sample, regions found in the same group (i.e., regions with same coordinates and grouping attribute values), are combined into a single region; this allows to merge regions that are duplicated inside the same sample (based on the values of their coordinates and of other possible specified region attributes). For each grouped region, it is possible to request the evaluation of aggregate functions on other region attributes (i.e., which are not coordinates, or grouping region attributes). This use is independent on the possible grouping realised based on metadata. The generated output schema only contains the original region attributes on which the grouping has been based, and additionally the attributes in case calculated as aggregated functions. If the group_by is applied only on regions, the output metadata and their values are equal to the ones in input. Both when applied on metadata and on regions, the group_by operation returns a number of output samples equal to the number of input ones. Note that the two possible uses of group_by, on metadata and on regions, are perfectly orthogonal, therefore they can be used in combination or independently.

### Usage

    ## S4 method for signature 'GMQLDataset'
    group_by(.data, groupBy_meta = conds(),
      groupBy_regions = c(""), region_aggregates = NULL,
      meta_aggregates = NULL)

### Arguments

`.data` | GMQLDataset object
`groupBy_meta` | `conds` function to support methods with groupBy or JoinBy input parameter
`groupBy_regions` | vector of strings made up by region attribute names
`region_aggregates` | It accepts a list of aggregate functions on region attribute. All the elements in the form key = aggregate. The aggregate is an object of class AGGREGATES. The aggregate functions available are: `SUM`, `COUNT`, `MIN`, `MAX`, `AVG`, `MEDIAN`, `STD`, `BAG`, `BAGD`, `Q1`, `Q2`, `Q3`. Every aggregate accepts a string value, except for COUNT, which does not have any value. Argument of 'aggregate function' must exist in schema, i.e. among region attributes. Two styles are allowed: list of key-value pairs: e.g. sum = SUM("pvalue") list of values: e.g. SUM("pvalue") "mixed style" is not allowed
`meta_aggregates` | It accepts a list of aggregate functions on metadata attribute. All the elements in the form key = aggregate. The aggregate is an object of class AGGREGATES. The aggregate functions available are: `SUM`, `COUNTSAMP`, `MIN`, `MAX`, `AVG`, `MEDIAN`, `STD`, `BAG`, `BAGD`, `Q1`, `Q2`, `Q3`. Every aggregate accepts a string value, except for COUNTSAMP, which does not have any value. Argument of 'aggregate function' must exist in schema, i.e. among region attributes. Two styles are allowed: list of key-value pairs: e.g. sum = SUM("cell") list of values: e.g. SUM("cell") "mixed style" is not allowed

### Value

GMQLDataset object. It contains the value to use as input for the subsequent GMQLDataset method

### Examples

    ## This statement initializes and runs the GMQL server for local execution
    ## and creation of results on disk. Then, with system.file() it defines
    ## the path to the folder "DATASET" in the subdirectory "example"
    ## of the package "RGMQL" and opens such file as a GMQL dataset named "exp"
    ## using CustomParser

    init_gmql()
    test_path <- system.file("example", "DATASET", package = "RGMQL")
    exp = read_gmql(test_path)

    ## This GMQL statement groups samples of the input 'exp' dataset according
    ## to their value of the metadata attribute 'tumor_type' and computes the
    ## maximum value that the metadata attribute 'size' takes inside the samples
    ## belonging to each group. The samples in the output GROUPS_T dataset
    ## have a new _group metadata attribute which indicates which group they
    ## belong to, based on the grouping on the metadata attribute tumor_type.
    ## In addition, they present the new metadata aggregate attribute 'MaxSize'.
    ## Note that the samples without metadata attribute 'tumor_type' are
    ## assigned to a single group with _group value equal 0

    GROUPS_T = group_by(exp, conds("tumor_type"),
        meta_aggregates = list(max_size = MAX("size")))

    ## This GMQL statement takes as input dataset the same input dataset as
    ## the previous example. Yet, it calculates new _group values based on the
    ## grouping attribute 'cell', and adds the metadata aggregate attribute
    ## 'n_samp', which counts the number of samples belonging to the respective
    ## group. It has the following output GROUPS_C dataset samples
    ## (note that now no sample has metadata attribute _group with value
    ## equal 0 since all input samples include the metadata attribute cell,
    ## with different values, on which the new grouping is based)

    GROUPS_C = group_by(exp, conds("cell"),
        meta_aggregates = list(n_samp = COUNTSAMP()))

    ## This GMQL statement groups the regions of each 'exp' dataset sample by
    ## region coordinates chr, left, right, strand  (these are implicitly
    ## considered) and the additional region attribute score (which is
    ## explicitly specified), and keeps only one region for each group.
    ## In the output GROUPS dataset schema, the new region attributes
    ## avg_pvalue and max_qvalue are added, respectively computed as the
    ## average of the values taken by the pvalue and the maximum of the values
    ## taken by the qvalue region attributes in the regions grouped together,
    ## and the computed value is assigned to each region of each output sample.
    ## Note that the region attributes which are not coordinates or score are
    ## discarded.

    GROUPS = group_by(exp, groupBy_regions = "score",
        region_aggregates = list(avg_pvalue = AVG("pvalue"),
        max_qvalue = MAX("qvalue")))

[Package RGMQL version 1.2.0 Index]