Statistics::Data - Load, access, update one or more data lists for statistical analysis


This is documentation for Version 0.11 of Statistics/, released Jan 2017.


 use Statistics::Data 0.11;
 my $dat = Statistics::Data->new();

 # with named arrays:
 $dat->load({'aname' => \@data1, 'anothername' => \@data2}); # names are arbitrary
 $aref = $dat->access(name => 'aname'); # gets back a copy of @data1
 $dat->add('aname' => [2, 3]); # pushes new values onto loaded copy of @data1
 $dat->dump_list(); # print to check if both arrays are loaded and their number of elements
 $dat->unload(name => 'anothername'); # only 'aname' data remains loaded
 $aref = $dat->access(name => 'aname'); # $aref is a reference to a copy of @data1
 $href = $dat->get_hoa(); # get all data
 $dat->dump_vals(name => 'aname', delim => ','); # proof in print it's back 

 # with multiple anonymous arrays:
 $dat->load(\@data1, \@data2); # any number of anonymous arrays
 $dat->add([2], [6]); # pushes a single value apiece onto copies of @data1 and @data2
 $aref = $dat->access(index => 1); # returns reference to copy of @data2, with its new values
 $dat->unload(index => 0); # only @data2 remains loaded, and its index is now 0


Handles data for some other statistics modules, as in loading, updating and retrieving data for analysis. Performs no actual statistical analysis itself.

Rationale is not wanting to write the same or similar load, add, etc. methods for every statistics module, not to provide an omnibus API for Perl stat modules. It, however, encompasses much of the variety of how Perl stats modules do the basic handling their data. Used for Statistics::Sequences (and its sub-tests).


Manages caches of one or more lists of data for use by some other statistics modules. The lists are ordered arrays comprised of literal scalars (numbers, strings). They can be loaded, added to (updated), accessed or unloaded by referring to the index (order) in which they have been loaded (or previously added to), or by a particular name. The lists are cached within the class object's '_DATA' aref as an aref itself, optionally associated with a 'name'. The particular structures supported here to load, update, retrieve, unload data are specified under load. Any module that uses this one as its base can still use its own rules to select the appropriate list, or provide the appropriate list within the call to itself.



 $dat = Statistics::Data->new();

Returns a new Statistics::Data object.


 $new_self = $dat->clone();

Alias: clone

Returns a copy of the class object with its data loaded (if any). This is not a copy of any particular data but the whole blessed hash; nothing modified in this new object affects the original.

Setting data

Methods to cache and uncache data into the data-object.


 $dat->load(ARRAY);             # CASE 1 - can be updated/retrieved anonymously, or as index => i (load order)
 $dat->load(AREF);            # CASE 2 - same, as aref
 $dat->load(STRING => AREF);    # CASE 3 - updated/retrieved as name => 'data' (arbitrary name); or by index (order)
 $dat->load({ STRING => AREF }) # CASE 4 - same as CASE 4, as hashref
 $dat->load(STRING => AREF, STRING => AREF);      # CASE 5 - same as CASE 3 but with multiple named loads
 $dat->load({ STRING => AREF, STRING => AREF });  # CASE 6 - same as CASE 5 bu as hashref
 $dat->load(AREF, AREF);  # CASE 7 - same as CASE 2 but with multiple aref loads

 # Not supported:
 #$dat->load(STRING => ARRAY); # not OK - use CASE 3 instead
 #$dat->load([AREF, AREF]); # not OK - use CASE 7 instead
 #$dat->load([ [STRING => AREF], [STRING => AREF] ]); # not OK - use CASE 5 or CASE 6 instead
 #$dat->load(STRING => AREF, STRING => [AREF, AREF]); # not OK - too mixed to make sense

Alias: load_data

Cache a list of data as an array-reference. Each call removes previous loads, as does sending nothing. If data need to be cached without unloading previous loads, use the add method instead. Arguments with the following structures are acceptable as data, and will be accessible by either index or name as expected:

load ARRAY

Load an anonymous array that has no named values. For example:

 $dat->load(1, 4, 7);

This is loaded as a single flat list, with an undefined name, and indexed as 0. Note that trying to load a named dataset with an unreferenced array is wrong - the name will be "folded" into the array itself.

load AREF

Load a reference to a single anonymous array that has no named values, e.g.:

 $dat->load([1, 4, 7]);

This is loaded as a single flat list, with an undefined name, and indexed as 0.

load ARRAY of AREF(s)

Same as above, but note that more than one unnamed array-reference can also be loaded at once, e.g.:

 $dat->load([1, 4, 7], [2, 5, 9]);
 $dat->load(\@ari1, \@ari2);

Each array can be accessed, using access, by specifying index => index, the latter value representing the order in which these arrays were loaded.

load HASH of AREF(s)

Load one or more named references to arrays, e.g.:

 $dat->load('dist1' => [1, 4, 7]);
 $dat->load('dist1' => [1, 4, 7], 'dist2' => [2, 5, 9]);

This loads the array(s) with a name attribute, so that when calling access, they can be retrieved by name, e.g., passing name => 'dist1'. The load method involves a check that there is an even number of arguments, and that, if this really is a hash, all the keys are defined and not empty, and all the values are in fact array-references.

load HASHREF of AREF(s)

As above, but where the hash is referenced, e.g.:

 $dat->load({'dist1' => [1, 4, 7], 'dist2' => [2, 5, 9]});

This means that using the following forms--including a referenced array of referenced arrays--will produce unexpected results, if they do not actually croak, and so should not be used:

 $dat->load(data => @data); # no croak but wrong - puts "data" in @data - use \@data
 $dat->load([\@blue_data, \@red_data]); # use unreferenced ARRAY of AREFs instead
 $dat->load([ [blues => \@blue_data], [reds => \@red_data] ]); # treated as single AREF; use HASH of AREFs instead
 $dat->load(blues => \@blue_data, reds => [\@red_data1, \@red_data2]); # mixed structures not supported

A warning is not thrown if any of the given arrays actually contain no data; could cause too many warnings if multiple analyses on different datasets are run.


Alias: add_data, append_data, update

Same usage as above for load. Just push any value(s) or so along, or loads an entirely named list, without clobbering what's already in there (as load would). If data have not been loaded with a name, then appending data to them happens according to the order of array-refs set here; e.g., $dat->add([], \new_data) adds nothing to the first loaded list, and initialises a second array, if none already, or appends the new data to it.


 $dat->unload(); # deletes all cached data, named or not
 $dat->unload(index => POSINT); # deletes the aref named 'data' whatever
 $dat->unload(name => STRING); # deletes the aref named 'data' whatever

Empty, clear, clobber what's in there. Does nothing if given index or name that does not refer to any loaded data. This should be used whenever any already loaded or added data are no longer required ahead of another add, including via copy or share.



Adds all the data from one Statistics::Data object to another. Changes in the new copies do not affect the originals.

Getting data


  $aref = $dat->get_aref(name => STRING);
  $aref = $dat->get_aref();

Returns a reference to a single, previously loaded hashref of arrayed of data, as specified in the named argument name. The array is empty if no data have been loaded, or if there is none with the given name. If name is not defined, and there is only one loaded array, a reference to that array is returned; otherwise croaks.


 $aref_of_arefs = $dat->get_aoa(name => AREF);
 $aref_of_arefs = $dat->get_aoa(); # all loaded data

Returns a reference to an array where each value is itself an array of data, as separately loaded under a different name or anonymously, in the order that they were loaded. If no name value is defined, all the loaded data are returned as a list of arefs.


  $href = $data->get_hoa(name => AREF); # 1 or more named data
  $href = $data->get_hoa(); # all named data
  %hash = $data->get_hoa(); # same but unreferenced

Returns a hash or hashref of arefs, where the keys are the names of the loaded data, and the values are arefs of their associated data.

By default, all of the loaded data are returned in the (reference to a) hash. The optional argument name is used to return one or more specific data-arrays in the hashref, given a referenced array of their names. Names that have never been used are ignored, and an empty hash (ref) is returned if all names are unknown, or there are no loaded data.


 $hoa = $dat->get_hoa_numonly_indep(name => AREF);
 $hoa = $dat->get_hoa_numonly_indep();

Same as get_hoa but each array is culled of any empty or non-numeric values as independent variables, with culls in one array not creating a cull on any other.


 $hoa = $dat->get_hoa_numonly_across(); # same as get_hoa but each list culled of NaNs at same i across lists

Returns hashref of previously loaded variable data (as arefs) culled of an empty or non-numerical values whereby a valid value in one list is culled if it is at an index that is invalid in another list. This is the type of data useful for a dependent ANOVA.


 $aref = $dat->access(); #returns the first and/or only array loaded, if any
 $aref = $dat->access(index => INT); #returns the ith array loaded
 $aref = $dat->access(name => STRING); # returns a particular named cache of data

Returns an aref given its index for order of being "added" to the loaded data, or by explicit name (as by get_aref). Default returned is the first loaded data, which is reliable if there is only one loaded array.


 $n = $dat->ndata();

Returns the number of loaded arrays.


 $aref = $dat->names();

Returns a reference to an array of all the datanames, if any.

Checking data


 $bool = $dat->all_full(AREF); # test data are valid before loading them
 $bool = $dat->all_full(name => STRING); # checking after loading/adding the data (or key in 'index')

Checks not only if the data array, as named or indexed, exists, but if it is non-empty: has no empty elements, with any elements that might exist in there being checked with hascontent.


 $bool = $dat->all_numeric(); # test data first-loaded, if any
 $bool = $dat->all_numeric(AREF); # test these data are valid before loading them
 $bool = $dat->all_numeric(name => STRING); # check specific data after loading/adding them by a 'name' or by their 'index' order
 ($aref, $bool) = $dat->all_numeric([3, '', 4.7, undef, 'b']); # returns ([3, 4.7], 0); - same for any loaded data

Given an aref of data, or reference to data previously loaded (see access), tests numeracy of each element, and return, if called in scalar context, a boolean scalar indicating if all data in this aref are defined and not empty (using nocontent in String::Util), and, if they have content, if these are all numerical, using looks_like_number in Scalar::Util. Alternatively, if called in list context, returns the data (as an aref) less any values that failed this test, followed by the boolean. If the requested data do not exist, returns undef.


 $bool = $dat->all_proportions(AREF); # test data are valid before loading them
 $bool = $dat->all_proportions(name => STRING); # checking after loading/adding the data  (or key in 'index')

Ensure data are all proportions. Sometimes, the data a module needs are all proportions, ranging from 0 to 1 inclusive. A dataset might have to be cleaned


 $bool = $dat->all_counts(AREF); # test data are valid before loading them
 $bool = $dat->all_counts(name => STRING); # checking after loading/adding the data  (or key in 'index')
 ($aref, $bool) = $dat->all_counts(AREF);

Returns true if all values in given data are real positive integers or zero, as well as satisfying "hascontent" and "looks_like_number" methods; false otherwise. Called in list context, returns aref of data culled of any values that are false on this basis, and then the boolean. For example, [2.2, 3, 4] and [-1, 3, 4] both fail, but [1, 3, 4] is true. Integer test is simply if $v == int($v).


 $bool = $dat->all_pos(AREF); # test data are valid before loading them
 $bool = $dat->all_pos(name => STRING); # checking after loading/adding the data  (or key in 'index')
 ($aref, $bool) = $dat->all_pos(AREF);

Returns true if all values in given data are greater than zero, as well as "hascontent" and "looks_like_number"; false otherwise. Called in list context, returns aref of data culled of any values that are false on this basis, and then the boolean.


 $num = $dat->equal_n(); # number of vals in each loaded data if equal; else 0
 $num = $dat->equal_n(name => AREF); # names of loaded data to check

If the named loaded data all have the same number of elements, then that number is returned; otherwise 0.

Dumping data


 $dat->dump_vals(delim => ", "); # assumes the first (only?) loaded array should be dumped
 $dat->dump_vals(index => INT, delim => ", "); # dump the i'th loaded array
 $dat->dump_vals(name => STRING, delim => ", "); # dump the array loaded/added with the given "name"

Prints to STDOUT a space-separated line (ending with "\n") of a loaded/added data's elements. Optionally, give a value for delim to specify how the elements in each array should be separated; default is a single space.


Dumps a list (using Text::SimpleTable) of the data currently loaded, without showing their actual elements. List is firstly by index, then by name (if any), then gives the number of elements in the associated array.


Don't know how to load/add the given data

Croaked when attempting to load or add data with an unsupported data structure where the first argument is a reference. See the examples under load for valid (and invalid) ways of sending data to them.

Data for accessing need to be loaded

Croaked when calling access, or any methods that use it internally -- viz., dump_vals and the validity checks all_numeric -- when it is called with a name for data that have not been loaded, or did not load successfully.

Data for unloading need to be loaded

Croaked when calling unload with an index or a name attribute and the data these refer to have not been loaded, or did not load successfully.

Data to get need to be named

Croaked when calling get_aref and no name is specified for the aref to get, and there is more than one loaded aref to choose from.


List::AllUtils - used for its all method when testing loads

Number::Misc - used for its is_even method when testing loads

String::Util - used for its hascontent and nocontent methods

Scalar::Util - required for all_numeric

Text::SimpleTable - required for dump_list


Please report any bugs or feature requests to bug-statistics-data-0.01 at, or through the web interface at This will notify the author, and then you'll automatically be notified of progress on your bug as any changes are made.


You can find documentation for this module with the perldoc command.

    perldoc Statistics::Data

You can also look for information at:


Roderick Garton, <rgarton at>


Copyright 2009-2017 Roderick Garton

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License. See for more information.