NAME

PDL::IO::CSV - Load/save PDL from/to CSV file (optimized for speed and large data)

SYNOPSIS

use PDL;
use PDL::IO::CSV ':all';

my $pdl = rcsv2D('input.csv');
$pdl *= 2;
wcsv2D($pdl, 'double.csv');

my ($pdl1, $pdl2, $pdl3) = rcsv1D('input.csv', [0, 1, 6]);
wcsv1D($pdl1, 'col2.csv');
#or
$pdl2->wcsv1D('col2.csv');
$pdl2->wcsv1D('col2_tabs.csv', {sep_char=>"\t"});

DESCRIPTION

The traditional way of creating PDL piddle from CSV data is via rcols function.

my $pdl = rcols("data.csv", [1..4], { DEFTYPE=>double, COLSEP=>"," });

This module provides alternative implementation based on Text::CSV_XS which should be significantly faster than traditional approach.

PDL::IO::CSV supports reading CSV data and creating PDL piddle(s) as well as saving PDL data to CSV file.

FUNCTIONS

By default, PDL::IO::CSV doesn't import any function. You can import individual functions like this:

use PDL::IO::CSV qw(rcsv2D wcsv2D);

Or import all available functions:

use PDL::IO::CSV ':all';

rcsv1D

Loads data from CSV file into 1D piddles (separate for each column).

my ($pdl1, $pdl2, $pdl3) = rcsv1D($csv_filename_or_filehandle);
#or
my ($pdl1, $pdl2, $pdl3) = rcsv1D($csv_filename_or_filehandle, \@column_ids);
#or
my ($pdl1, $pdl2, $pdl3) = rcsv1D($csv_filename_or_filehandle, \%options);
#or
my ($pdl1, $pdl2, $pdl3) = rcsv1D($csv_filename_or_filehandle, \@column_ids, \%options);

Parameters:

• csv_filename_or_filehandle

  Path to CSV file to be loaded or a filehandle open for reading.

• column_ids

  Optional column indices (0-based) defining which columns to load from CSV file. Default is undef which means to load all columns.

Items supported in options hash:

• type

  Defines the type of output piddles: double, float, longlong, long, short, byte. Default value is double. BEWARE: type `longlong` can be used only on perls with 64bitint support.

  You can set one type for all columns/piddles:

    my ($a, $b, $c) = rcsv1D($csv, {type => double});
  

  or separately for each column/piddle:

    my ($a, $b, $c) = rcsv1D($csv, {type => [long, double, double]});
  

  Special datetime handling (you need to have PDL::DateTime installed):

    my ($a, $b, $c) = rcsv1D($csv, {type => [long, 'datetime', double]});
    # piddle $b will be an instance of PDL::DateTime
  

  or

    my ($a, $b, $c) = rcsv1D($csv, {type => [long, '%m/%d/%Y', double]});
    # piddle $b will be an instance of PDL::DateTime
  

  or you cat let PDL::IO::CSV try to detect datetime columns (detection is based only on the first csv line)

    my ($a, $b, $c) = rcsv1D($csv, {detect_datetime=>1});
  

• detect_datetime

  Values 1 (default) or 0. Try to detect datetime columns, corresponding output piddles will be instances of PDL::Datetime (which you need to have installed).

  Value 1 means: try to detect datetime in ISO8601 format, e.g. '2016-12-16 11:59'.

  You can also specify a value as strptime format string, e.g. '%m/%d/%Y %H:%M:%S'.

• fetch_chunk

  We do not try to load all CSV data into memory at once; we load them in chunks defined by this parameter. Default value is 40000 (CSV rows).

• reshape_inc

  As we do not try to load the whole CSV file into memory at once, we also do not know at the beginning how many rows there will be. Therefore we do not know how big piddle to allocate, we have to incrementally (re)allocated the piddle by increments defined by this parameter. Default value is 80000.

  If you know how many rows there will be you can improve performance by setting this parameter to expected row count.

• empty2bad

  Values 0 (default) or 1 - convert empty cells to BAD values (there is a performance cost when turned on). If not enabled the empty values are silently converted into 0.

• text2bad

  Values 0 (default) or 1 - convert values that don't pass looks_like_number check to BAD values (there is a significant performance cost when turned on). If not enabled these non-numerical values are silently converted into 0.

• header

  Values 0 or N (positive integer) - consider the first N lines as headers and skip them. BEWARE: we are talking here about skipping CSV lines which in some cases might be more than 1 text line.

  NOTE: header values (if any) are considered to be column names and are stored in loaded piddles in $pdl->hdr->{col_name}

  NOTE: rcsv1D accepts a special header value 'auto' which skips rows (from beginning) that have in all columns non-numeric values.

  Default: for rcsv1D - 'auto'; for rcsv2D - 0.

• decimal_comma

  Values 0 (default) or 1 - accept , (comma) as a decimal separator (there is a performance cost when turned on).

• encoding

  Optional enconding e.g. :utf8 (default undef) that will be applied on input filehandle.

• debug

  Values 0 (default) or 1 - turn on/off debug messages

• sep_char

  Value separator, default value , (comma).

• and all other options valid for new method of Text::CSV_XS

rcsv2D

Loads data from CSV file into 2D piddle.

my $pdl = rcsv2D($csv_filename_or_filehandle);
#or
my $pdl = rcsv2D($csv_filename_or_filehandle, \@column_ids);
#or
my $pdl = rcsv2D($csv_filename_or_filehandle, \%options);
#or
my $pdl = rcsv2D($csv_filename_or_filehandle, \@column_ids, \%options);

Parameters and items supported in options hash are the same as by "rcsv1D".

wcsv1D

Saves data from one or more 1D piddles to CSV file.

wcsv1D($pdl1, $pdl2, $pdl3, $csv_filename_or_filehandle, \%options);
#or
wcsv1D($pdl1, $pdl2, $pdl3, $csv_filename_or_filehandle);
#or
wcsv1D($pdl1, $pdl2, \%options); #prints to STDOUT
#or
wcsv1D($pdl1, $pdl2);

# but also as a piddle method
$pdl1D->wcsv1D("file.csv");

NOTE: piddles piddles are instances of PDL::DateTime are exported by wcsv1D as ISO 8601 strings.

Parameters:

• piddles

  One or more 1D piddles. All has to be 1D but may have different count of elements.

• csv_filename_or_filehandle

  Path to CSV file to write to or a filehandle open for writing. Default is STDOUT.

Items supported in options hash:

• header

  Arrayref with values that will be printed as the first CSV line. Or 'auto' value which means that column names are taken from $pdl->hdr->{col_name}.

  Default: for wcsv1D - 'auto'; for wcsv2D - undef.

• bad2empty

  Values 0 or 1 (default) - convert BAD values into empty strings (there is a performance cost when turned on).

• encoding

  Optional enconding e.g. :utf8 (default undef) that will be applied on output filehandle.

• debug

  Values 0 (default) or 1 - turn on/off debug messages

• sep_char

  Value separator, default value , (comma).

• eol

  New line separator, default value \n (UNIX newline).

• and all other options valid for new method of Text::CSV_XS

wcsv2D

Saves data from one 2D piddle to CSV file.

wcsv2D($pdl, $csv_filename_or_filehandle, \%options);
#or
wcsv2D($pdl, $csv_filename_or_filehandle);
#or
wcsv2D($pdl, \%options); #prints to STDOUT
#or
wcsv2D($pdl);

# but also as a piddle method
$pdl->wcsv2D("file.csv");

Parameters and items supported in options hash are the same as by "wcsv1D".

SEE ALSO

PDL, Text::CSV_XS

LICENSE

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

COPYRIGHT

2014+ KMX kmx@cpan.org