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.\" ========================================================================
.\"
.IX Title "HDF5::Dataset 3pm"
.TH HDF5::Dataset 3pm "2022-11-30" "perl v5.36.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
PDL::IO::HDF5::Dataset \- PDL::IO::HDF5 Helper Object representing HDF5 datasets.
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This is a helper-object used by \s-1PDL::IO::HDF5\s0 to interface with \s-1HDF5\s0 format's dataset objects.
Information on the \s-1HDF5\s0 Format can be found
at the \s-1HDF\s0 Group's web site at http://www.hdfgroup.org .
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
See \s-1PDL::IO::HDF5\s0
.SH "MEMBER DATA"
.IX Header "MEMBER DATA"
.IP "\s-1ID\s0" 1
.IX Item "ID"
\&\s-1ID\s0 number given to the dataset by the \s-1HDF5\s0 library
.IP "name" 1
.IX Item "name"
Name of the dataset.
.IP "parent" 1
.IX Item "parent"
Ref to parent object (group) that owns this dateset.
.IP "fileObj" 1
.IX Item "fileObj"
Ref to the \s-1PDL::IO::HDF5\s0 object that owns this object.
.SH "METHODS"
.IX Header "METHODS"
####\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
.SS "new"
.IX Subsection "new"
PDL::IO::HDF5::Dataset Constructor \- creates new object
.PP
\&\fBUsage:\fR
.PP
This object will usually be created using the calling format detailed in the \s-1SYNOPSIS\s0. The 
following syntax is used by the \s-1PDL::IO::HDF5\s0 object to build the object.
.PP
.Vb 6
\&   $a = new PDL::IO::HDF5:Dataset( name => $name, parent => $parent, 
\&                                fileObj => $fileObj);
\&        Args:
\&        $name                           Name of the dataset
\&        $parent                         Parent Object that owns this dataset
\&        $fileObj                        PDL::HDF object that owns this dateset.
.Ve
.SS "\s-1DESTROY\s0"
.IX Subsection "DESTROY"
PDL::IO::HDF5::Dataset Destructor \- Closes the dataset object
.PP
\&\fBUsage:\fR
.PP
.Vb 1
\&   No Usage. Automatically called
.Ve
.SS "set"
.IX Subsection "set"
Write data to the \s-1HDF5\s0 dataset
.PP
\&\fBUsage:\fR
.PP
.Vb 1
\& $dataset\->set($pdl, unlimited => 1);     # Write the array data in the dataset
\&
\&     Options:
\&     unlimited     If present, the dataset is created with unlimited dimensions.
.Ve
.SS "get"
.IX Subsection "get"
Get data from a \s-1HDF5\s0 dataset to a \s-1PDL\s0
.PP
\&\fBUsage:\fR
.PP
.Vb 2
\& $pdl = $dataset\->get;     # Read the Array from the HDF5 dataset, create a PDL from it
\&                           #  and put in $pdl
\&
\&                           # Assuming $dataset is three dimensional
\&                           # with dimensions (20,100,90)
.Ve
.PP
The \fIget\fR method can also be used to obtain particular slices or hyperslabs
of the dataset array. For example, if \f(CW$dataset\fR is three dimensional with dimensions
(20,100,90) then we could do:
.PP
.Vb 3
\& $start=pdl([0,0,0]);      # We begin the slice at the very beginning
\& $end=pdl([19,0,0]);       # We take the first vector of the array,
\& $stride=pdl([2,1,1]);     # taking only every two values of the vector 
\&
\& $pdl = $dataset\->get($start,$end,[$stride]); # Read a slice or
\&                           # hyperslab from the HDF5 dataset.
\&                           # $start, $end and optionally $stride
\&                           # should be PDL vectors with length the
\&                           # number of dimensions of the dataset.
\&                           # $start gives the starting coordinates
\&                           # in the array.
\&                           # $end gives the ending coordinate
\&                           # in the array
\&                           # $stride gives the steps taken from one
\&                           # coordinate to the next of the slice
.Ve
.PP
The mapping of \s-1HDF5\s0 datatypes in the file to \s-1PDL\s0 datatypes in memory will be according
to the following table.
.PP
.Vb 10
\& HDF5 File Type                         PDL Type
\& \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-               \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
\& PDL::IO::HDF5::H5T_C_S1()      =>      PDL::Char Object    (Special Case for Char Strings)
\& PDL::IO::HDF5::H5T_STD_I8BE()  =>      $PDL::Types::PDL_B
\& PDL::IO::HDF5::H5T_STD_I8LE()  =>      $PDL::Types::PDL_B,
\& PDL::IO::HDF5::H5T_STD_U8BE()  =>      $PDL::Types::PDL_S,
\& PDL::IO::HDF5::H5T_STD_U8LE()  =>      $PDL::Types::PDL_S,
\& PDL::IO::HDF5::H5T_STD_I16BE() =>      $PDL::Types::PDL_S,
\& PDL::IO::HDF5::H5T_STD_I16LE() =>      $PDL::Types::PDL_S,
\& PDL::IO::HDF5::H5T_STD_U16BE() =>      $PDL::Types::PDL_L,
\& PDL::IO::HDF5::H5T_STD_U16LE() =>      $PDL::Types::PDL_L,
\& PDL::IO::HDF5::H5T_STD_I32BE() =>      $PDL::Types::PDL_L,
\& PDL::IO::HDF5::H5T_STD_I32LE() =>      $PDL::Types::PDL_L,
\& PDL::IO::HDF5::H5T_STD_U32LE() =>      $PDL::Types::PDL_LL,
\& PDL::IO::HDF5::H5T_STD_U32BE() =>      $PDL::Types::PDL_LL,
\& PDL::IO::HDF5::H5T_STD_I64LE() =>      $PDL::Types::PDL_LL,
\& PDL::IO::HDF5::H5T_STD_I64BE() =>      $PDL::Types::PDL_LL,
\& PDL::IO::HDF5::H5T_IEEE_F32BE()=>      $PDL::Types::PDL_F,
\& PDL::IO::HDF5::H5T_IEEE_F32LE()=>      $PDL::Types::PDL_F,
\& PDL::IO::HDF5::H5T_IEEE_F64BE()=>      $PDL::Types::PDL_D,
\& PDL::IO::HDF5::H5T_IEEE_F64LE()=>      $PDL::Types::PDL_D
.Ve
.PP
For \s-1HDF5\s0 File types not in this table, this method will attempt to
map it to the default \s-1PDL\s0 type \s-1PDL_D.\s0
.PP
If the dataset being read is a scalar reference, the referenced dataset region will be read instead.
.PP
\&\fBNote:\fR
.PP
Character arrays are returned as the special PDL::Char fixed-length string type. For fixed-length
\&\s-1HDF5\s0 string arrays, this is a direct mapping to the PDL::Char datatype. For \s-1HDF5\s0 variable-length string
arrays, the data is converted to a fixed-length character array, with a string size equal to the maximum
size of all the strings in the array.
.SS "dims"
.IX Subsection "dims"
Get the dims for a \s-1HDF5\s0 dataset. For example, a 3 x 4 array would return a perl array
(3,4);
.PP
\&\fBUsage:\fR
.PP
.Vb 1
\& @pdl = $dataset\->dims;    # Get an array of dims.
.Ve
.SS "attrSet"
.IX Subsection "attrSet"
Set the value of an attribute(s)
.PP
Attribute types supported are null-terminated strings and \s-1PDL\s0 matrices
.PP
\&\fBUsage:\fR
.PP
.Vb 7
\&   $dataset\->attrSet( \*(Aqattr1\*(Aq => \*(Aqattr1Value\*(Aq,
\&                    \*(Aqattr2\*(Aq => \*(Aqattr2 value\*(Aq, 
\&                    \*(Aqattr3\*(Aq => $pdl,
\&                    .
\&                    .
\&                    .
\&                   );
.Ve
.PP
Returns undef on failure, 1 on success.
.SS "attrDel"
.IX Subsection "attrDel"
Delete attribute(s)
.PP
\&\fBUsage:\fR
.PP
.Vb 6
\& $dataset\->attrDel( \*(Aqattr1\*(Aq, 
\&                    \*(Aqattr2\*(Aq,
\&                    .
\&                    .
\&                    .
\&                   );
.Ve
.PP
Returns undef on failure, 1 on success.
.SS "attrs"
.IX Subsection "attrs"
Get a list of all attribute names associated with a dataset
.PP
\&\fBUsage:\fR
.PP
.Vb 1
\&   @attrs = $dataset\->attrs;
.Ve
.SS "attrGet"
.IX Subsection "attrGet"
Get the value of an attribute(s)
.PP
Currently the attribute types supported are null-terminated strings
and PDLs.
.PP
\&\fBUsage:\fR
.PP
.Vb 1
\&   my @attrs = $dataset\->attrGet( \*(Aqattr1\*(Aq, \*(Aqattr2\*(Aq);
.Ve
.SS "IDget"
.IX Subsection "IDget"
Returns the \s-1HDF5\s0 library \s-1ID\s0 for this object
.PP
\&\fBUsage:\fR
.PP
.Vb 1
\& my $ID = $dataSetObj\->IDget;
.Ve
.SS "nameGet"
.IX Subsection "nameGet"
Returns the \s-1HDF5\s0 Dataset Name for this object.
.PP
\&\fBUsage:\fR
.PP
.Vb 1
\& my $name = $datasetObj\->nameGet;
.Ve