reduceDataFrame {QFeatures} | R Documentation

## Reduces and expands a `DataFrame`

### Description

A long dataframe can be reduced by mergeing certain rows into a single one. These new variables are constructed as a `SimpleList` containing all the original values. Invariant columns, i.e columns that have the same value along all the rows that need to be merged, can be shrunk into a new variables containing that invariant value (rather than in list columns). The grouping of rows, i.e. the rows that need to be shrunk together as one, is defined by a vector.

The opposite operation is expand. But note that for a `DataFrame` to be expanded back, it must not to be simplified.

### Usage

    reduceDataFrame(x, k, count = FALSE, simplify = TRUE, drop = FALSE)

    expandDataFrame(x, k = NULL)

### Arguments

`x` | The `DataFrame` to be reduced or expanded.
`k` | A ‘vector’ of length `nrow(x)` defining the grouping based on which the `DataFrame` will be shrunk.
`count` | `logical(1)` specifying of an additional column (called by default `.n`) with the tally of rows shrunk into on new row should be added. Note that if already existing, `.n` will be silently overwritten.
`simplify` | A `logical(1)` defining if invariant columns should be converted to simple lists. Default is `TRUE`.
`drop` | A `logical(1)` specifying whether the non-invariant columns should be dropped altogether. Default is `FALSE`.

### Value

An expanded (reduced) `DataFrame`.

### Missing values

Missing values do have an important effect on `reduce`. Unless all values to be reduces are missing, they will result in an non-invariant column, and will be dropped with `drop = TRUE`. See the example below.

The presence of missing values can have side effects in higher level functions that rely on reduction of `DataFrame` objects.

### Author(s)

Laurent Gatto

### Examples

    library("IRanges")

    k <- sample(100, 1e3, replace = TRUE)
    df <- DataFrame(k = k,
                    x = round(rnorm(length(k)), 2),
                    y = seq_len(length(k)),
                    z = sample(LETTERS, length(k), replace = TRUE),
                    ir = IRanges(seq_along(k), width = 10),
                    r = Rle(sample(5, length(k), replace = TRUE)),
                    invar = k + 1)
    df

    ## Shinks the DataFrame
    df2 <- reduceDataFrame(df, df$k)
    df2

    ## With a tally of the number of members in each group
    reduceDataFrame(df, df$k, count = TRUE)

    ## Much faster, but more crowded result
    df3 <- reduceDataFrame(df, df$k, simplify = FALSE)
    df3

    ## Drop all non-invariant columns
    reduceDataFrame(df, df$k, drop = TRUE)

    ## Missing values
    d <- DataFrame(k = rep(1:3, each = 3),
                   x = letters[1:9],
                   y = rep(letters[1:3], each = 3),
                   y2 = rep(letters[1:3], each = 3))
    d

    ## y is invariant and can be simplified
    reduceDataFrame(d, d$k)
    ## y isn't not dropped
    reduceDataFrame(d, d$k, drop = TRUE)

    ## BUT with a missing value
    d[1, "y"] <- NA
    d

    ## y isn't invariant/simplified anymore
    reduceDataFrame(d, d$k)
    ## y now gets dropped
    reduceDataFrame(d, d$k, drop = TRUE)

[Package QFeatures version 1.2.0 Index]