writeTENxMatrix {HDF5Array} | R Documentation

## Write a matrix-like object as an HDF5-based sparse matrix

### Description

The 1.3 Million Brain Cell Dataset and other datasets published by 10x Genomics use an HDF5-based sparse matrix representation instead of the conventional (i.e. dense) HDF5 representation.

`writeTENxMatrix` writes a matrix-like object to this format.

IMPORTANT NOTE: Only use `writeTENxMatrix` if the matrix-like object to write is sparse, that is, if most of its elements are zero. Using `writeTENxMatrix` on dense data is very inefficient! In this case, you should use `writeHDF5Array` instead.

### Usage

    writeTENxMatrix(x, filepath=NULL, group=NULL, level=NULL, verbose=FALSE)

### Arguments

`x` | The matrix-like object to write to an HDF5 file. The object to write should typically be sparse, that is, most of its elements should be zero. If `x` is a DelayedMatrix object, `writeTENxMatrix` realizes it on disk, that is, all the delayed operations carried by the object are executed while the object is written to disk.
`filepath` | `NULL` or the path (as a single string) to the (new or existing) HDF5 file where to write the data. If `NULL`, then the data will be written to the current HDF5 dump file i.e. to the file whose path is `getHDF5DumpFile`.
`group` | `NULL` or the name of the HDF5 group where to write the data. If `NULL`, then the name returned by `getHDF5DumpName` will be used.
`level` | The compression level to use for writing the data to disk. By default, `getHDF5DumpCompressionLevel()` will be used. See `?getHDF5DumpCompressionLevel` for more information.
`verbose` | Set to `TRUE` to make the function display progress.

### Details

Please note that, depending on the size of the data to write to disk and the performance of the disk, `writeTENxMatrix` can take a long time to complete. Use `verbose=TRUE` to see its progress.

Use `setHDF5DumpFile` and `setHDF5DumpName` to control the location of automatically created HDF5 datasets.

### Value

A TENxMatrix object pointing to the newly written HDF5 data on disk.

### See Also

- TENxMatrix objects.

- The `TENxBrainData` dataset (in the TENxBrainData package).

- HDF5-dump-management to control the location and physical properties of automatically created HDF5 datasets.

- `h5ls` in the rhdf5 package.

### Examples

    ## ---------------------------------------------------------------------
    ## A SIMPLE EXAMPLE
    ## ---------------------------------------------------------------------
    m0 <- matrix(0L, nrow=25, ncol=12,
                 dimnames=list(letters[1:25], LETTERS[1:12]))
    m0[cbind(2:24, c(12:1, 2:12))] <- 100L + sample(55L, 23, replace=TRUE)
    out_file <- tempfile()
    M0 <- writeTENxMatrix(m0, out_file, group="m0")
    M0
    sparsity(M0)

    path(M0)  # same as 'out_file'

    ## Use the h5ls() command from the rhdf5 package to see the structure of
    ## the file:
    library(rhdf5)
    h5ls(path(M0))

    ## ---------------------------------------------------------------------
    ## USING THE "1.3 Million Brain Cell Dataset"
    ## ---------------------------------------------------------------------

    ## The 1.3 Million Brain Cell Dataset from 10x Genomics is available via
    ## ExperimentHub:
    library(ExperimentHub)
    hub <- ExperimentHub()
    query(hub, "TENxBrainData")
    fname <- hub[["EH1039"]]
    oneM <- TENxMatrix(fname, "mm10")  # see ?TENxMatrix for the details
    oneM

    ## Note that the following transformation preserves sparsity:
    M2 <- log(oneM + 1)  # delayed
    M2                   # a DelayedMatrix instance

    ## In order to reduce computation times, we'll write only the first
    ## 5000 columns of M2 to disk:
    out_file <- tempfile()
    M3 <- writeTENxMatrix(M2[ , 1:5000], out_file, group="mm10", verbose=TRUE)
    M3                   # a TENxMatrix instance

[Package HDF5Array version 1.12.3 Index]