- NAME
- VERSION
- SYNOPSIS
- EXPORT
- DESCRIPTION
- CONVENTIONS USED
- DATASET STRUCTURE
- PERCEPTRON DATA
- DATA PROCESSING RELATED SUBROUTINES
  - shuffle_stimuli ( ... )
  - shuffle_data ( $original_data => $shuffled_1, $shuffled_2, ... )
  - shuffle_data ( ORIGINAL_DATA, $shuffled_1, $shuffled_2, ... )
- CREATION RELATED SUBROUTINES/METHODS
  - new ( \%options )
  - get_attributes
  - learning_rate ( $value )
  - learning_rate
  - threshold ( $value )
  - threshold
- TRAINING RELATED SUBROUTINES/METHODS
  - tame ( ... )
  - exercise ( ... )
  - train ( $stimuli_train_csv, $expected_output_header, $save_nerve_to_file )
  - train ( $stimuli_train_csv, $expected_output_header, $save_nerve_to_file, $display_stats, $identifier )
  - &_calculate_output( $self, \%stimuli_hash )
  - &_tune( $self, \%stimuli_hash, $tune_up_or_down )
- VALIDATION RELATED METHODS
  - take_mock_exam (...)
  - take_lab_test (...)
  - validate ( \%options )
- TESTING RELATED SUBROUTINES/METHODS
  - take_real_exam (...)
  - work_in_real_world (...)
  - test ( \%options )
  - _real_validate_or_test ( $data_hash_ref )
  - &_fill_predicted_values ( $self, $stimuli_validate, $predicted_index, $aoa )
- RESULTS RELATED SUBROUTINES/METHODS
  - get_exam_results ( ... )
  - get_confusion_matrix ( \%options )
  - &_collect_stats ( \%options )
  - &_calculate_total_entries ( $c_matrix_ref )
  - &_calculate_accuracy ( $c_matrix_ref )
  - &_calculate_sensitivity ( $c_matrix_ref )
  - &_calculate_precision ( $c_matrix_ref )
  - &_calculate_specificity ( $c_matrix_ref )
  - &_calculate_f1_score ( $c_matrix_ref )
  - &_calculate_negative_predicted_value( $c_matrix_ref )
  - &_calculate_false_negative_rate( $c_matrix_ref )
  - &_calculate_false_positive_rate( $c_matrix_ref )
  - &_calculate_false_discovery_rate( $c_matrix_ref )
  - &_calculate_false_omission_rate( $c_matrix_ref )
  - &_calculate_balanced_accuracy( $c_matrix_ref )
  - display_exam_results ( ... )
  - display_confusion_matrix ( \%confusion_matrix, \%labels )
  - &_build_matrix ( $c_matrix, $labels )
  - &_print_extended_matrix ( $matrix, $c_matrix )
- NERVE DATA RELATED SUBROUTINES
  - preserve ( ... )
  - save_perceptron ( $nerve, $nerve_file )
  - revive (...)
  - load_perceptron ( $nerve_file_to_load )
- NERVE PORTABILITY RELATED SUBROUTINES
  - preserve_as_yaml ( ... )
  - save_perceptron_yaml ( $nerve, $yaml_nerve_file )
  - revive_from_yaml (...)
  - load_perceptron_yaml ( $yaml_nerve_file )
- TO DO
- KNOWN ISSUES
  - Portability of Nerve Data
- AUTHOR
- BUGS
- SUPPORT
- ACKNOWLEDGEMENTS
- SEE ALSO
- LICENSE AND COPYRIGHT

# NAME

AI::Perceptron::Simple

A Newbie Friendly Module to Create, Train, Validate and Test Perceptrons / Neurons

# VERSION

Version 1.04

# SYNOPSIS

        #!/usr/bin/perl

        use AI::Perceptron::Simple qw(...);

        # create a new nerve / neuron / perceptron
        $nerve = AI::Perceptron::Simple->new( {
            initial_value => $size_of_each_dendrite,
            learning_rate => 0.3, # optional
            threshold => 0.85, # optional
            attribs => \@dendrites,
        } );

        # train
        $nerve->tame( ... );
        $nerve->exercise( ... );
        $nerve->train( $training_data_csv, $expected_column_name, $save_nerve_to );
        # or
        $nerve->train(
            $training_data_csv, $expected_column_name, $save_nerve_to,
            $show_progress, $identifier); # these two parameters must go together

        # validate
        $nerve->take_lab_test( ... );
        $nerve->take_mock_exam( ... );

        # fill results to original file
        $nerve->validate( {
            stimuli_validate => $validation_data_csv,
            predicted_column_index => 4,
         } );
        # or
        # fill results to a new file
        $nerve->validate( {
            stimuli_validate => $validation_data_csv,
            predicted_column_index => 4,
            results_write_to => $new_csv
        } );

        # test - see "validate" method, same usage
        $nerve->take_real_exam( ... );
        $nerve->work_in_real_world( ... );
        $nerve->test( ... );

        # confusion matrix
        my %c_matrix = $nerve->get_confusion_matrix( {
            full_data_file => $file_csv,
            actual_output_header => $header_name,
            predicted_output_header => $predicted_header_name,
            more_stats => 1, # optional
        } );

        # accessing the confusion matrix
        my @keys = qw( true_positive true_negative false_positive false_negative
                       total_entries accuracy sensitivity );
        for ( @keys ) {
            print $_, " => ", $c_matrix{ $_ }, "\n";
        }

        # output to console
        $nerve->display_confusion_matrix( \%c_matrix, {
            zero_as => "bad apples", # cat  milk   green  etc.
            one_as => "good apples", # dog  honey  pink   etc.
        } );

        # saving and loading data of perceptron locally
        # NOTE: nerve data is automatically saved after each trainning process
        use AI::Perceptron::Simple ":local_data";

        my $nerve_file = "apples.nerve";
        preserve( ... );
        save_perceptron( $nerve, $nerve_file );

        # load data of percpetron for use in actual program
        my $apple_nerve = revive( ... );
        my $apple_nerve = load_perceptron( $nerve_file );

        # for portability of nerve data
        use AI::Perceptron::Simple ":portable_data";

        my $yaml_nerve_file = "pearls.yaml";
        preserve_as_yaml ( ... );
        save_perceptron_yaml ( $nerve, $yaml_nerve_file );

        # load nerve data on the other computer
        my $pearl_nerve = revive_from_yaml ( ... );
        my $pearl_nerve = load_perceptron_yaml ( $yaml_nerve_file );

        # processing data
        use AI::Perceptron::Simple ":process_data";
        shuffle_stimuli ( ... )
        shuffle_data ( ORIGINAL_STIMULI, $new_file_1, $new_file_2, ... );
        shuffle_data ( $original_stimuli => $new_file_1, $new_file_2, ... );

# EXPORT

None by default.

All the subroutines from `DATA PROCESSING RELATED SUBROUTINES`, `NERVE DATA RELATED SUBROUTINES` and `NERVE PORTABILITY RELATED SUBROUTINES` sections are importable through tags or manually specifying them.

The tags available include the following:

`:process_data` - subroutines under `DATA PROCESSING RELATED SUBROUTINES` section.
`:local_data` - subroutines under `NERVE DATA RELATED SUBROUTINES` section.
`:portable_data` - subroutines under `NERVE PORTABILITY RELATED SUBROUTINES` section.

Most of the stuff are OO.

# DESCRIPTION

This module provides methods to build, train, validate and test a perceptron. It can also save the data of the perceptron for future use for any actual AI programs.

This module is also aimed to help newbies grasp hold of the concept of perceptron, training, validation and testing as much as possible. Hence, all the methods and subroutines in this module are decoupled as much as possible so that the actual scripts can be written as simple complete programs.

The implementation here is super basic as it only takes in input of the dendrites and calculate the output. If the output is higher than the threshold, the final result (category) will be 1 aka perceptron is activated. If not, then the result will be 0 (not activated).

Depending on how you view or categorize the final result, the perceptron will fine tune itself (aka train) based on the learning rate until the desired result is met. Everything from here on is all mathematics and numbers which only makes sense to the computer and not humans anymore.

Whenever the perceptron fine tunes itself, it will increase/decrease all the dendrites that is significant (attributes labelled 1) for each input. This means that even when the perceptron successfully fine tunes itself to suite all the data in your file for the first round, the perceptron might still get some of the things wrong for the next round of training. Therefore, the perceptron should be trained for as many rounds as possible. The more "confusion" the perceptron is able to correctly handle, the more "mature" the perceptron is. No one defines how "mature" it is except the programmer himself/herself :)

# CONVENTIONS USED

Please take note that not all subroutines/method must be used to make things work. All the subroutines and methods are listed out for the sake of writing the documentation.

Private methods/subroutines are prefixed with `_` or `&_` and they aren't meant to be called directly. You can if you want to. There are quite a number of them to be honest, just ignore them if you happen to see them :)

Synonyms are placed before the actual ie. technical subroutines/methods. You will see `...` as the parameters if they are synonyms. Move to the next subroutine/method until you find something like `\%options` as the parameter or anything that isn't `...` for the description.

# DATASET STRUCTURE

This module can only process CSV files.

Any field ie columns that will be used for processing must be binary ie. `0` or `1` only. Your dataset can contain other columns with non-binary data as long as they are not one of the dendrites.

There are soem sample dataset which can be found in the `t` directory. The original dataset can also be found in `docs/book_list.csv`. The files can also be found here.

# PERCEPTRON DATA

The perceptron/neuron data is stored using the `Storable` module.

See `Portability of Nerve Data` section below for more info on some known issues.

# DATA PROCESSING RELATED SUBROUTINES

These subroutines can be imported using the tag `:process_data`.

These subroutines should be called in the procedural way.

## shuffle_stimuli ( ... )

The parameters and usage are the same as `shuffled_data`. See the next two subroutines.

## shuffle_data ( $original_data => $shuffled_1, $shuffled_2, ... )

## shuffle_data ( ORIGINAL_DATA, $shuffled_1, $shuffled_2, ... )

Shuffles `$original_data` or `ORIGINAL_DATA` and saves them to other files.

# CREATION RELATED SUBROUTINES/METHODS

## new ( \%options )

Creates a brand new perceptron and initializes the value of each attribute / dendrite aka. weight. Think of it as the thickness or plasticity of the dendrites.

For `%options`, the followings are needed unless mentioned:

initial_value => $decimal

  The value or thickness of ALL the dendrites when a new perceptron is created.

  Generally speaking, this value is usually between 0 and 1. However, it all depend on your combination of numbers for the other options.

attribs => $array_ref

  An array reference containing all the attributes / dendrites names. Yes, give them some names :)

learning_rate => $decimal

  Optional. The default is `0.05`.

  The learning rate of the perceptron for the fine-tuning process.

  This value is usually between 0 and 1. However, it all depends on your combination of numbers for the other options.

threshold => $decimal

  Optional. The default is `0.5`

  This is the passing rate to determine the neuron output (`0` or `1`).

  Generally speaking, this value is usually between `0` and `1`. However, it all depend on your combination of numbers for the other options.

## get_attributes

Obtains a hash of all the attributes of the perceptron

## learning_rate ( $value )

## learning_rate

If `$value` is given, sets the learning rate to `$value`. If not, then it returns the learning rate.

## threshold ( $value )

## threshold

If `$value` is given, sets the threshold / passing rate to `$value`. If not, then it returns the passing rate.

# TRAINING RELATED SUBROUTINES/METHODS

All the training methods here have the same parameters as the two actual `train` method and they all do the same stuff. They are also used in the same way.

## tame ( ... )

## exercise ( ... )

## train ( $stimuli_train_csv, $expected_output_header, $save_nerve_to_file )

## train ( $stimuli_train_csv, $expected_output_header, $save_nerve_to_file, $display_stats, $identifier )

Trains the perceptron.

`$stimuli_train_csv` is the set of data / input (in CSV format) to train the perceptron while `$save_nerve_to_file` is the filename that will be generate each time the perceptron finishes the training process. This data file is the data of the `AI::Perceptron::Simple` object and it is used in the `validate` method.

`$expected_output_header` is the header name of the columns in the csv file with the actual category or the exepcted values. This is used to determine to tune the nerve up or down. This value should only be 0 or 1 for the sake of simplicity.

`$display_stats` is optional and the default is 0. It will display more output about the tuning process. It will show the followings:

tuning status

  Indicates the nerve was tuned up, down or no tuning needed

old sum

  The original sum of all `weightage * input` or `dendrite_size * binary_input`

threshold

  The threshold of the nerve

new sum

  The new sum of all `weightage * input` after fine-tuning the nerve

If `$display_stats` is specified ie. set to `1`, then you MUST specify the `$identifier`. `$identifier` is the column / header name that is used to identify a specific row of data in `$stimuli_train_csv`.

## &_calculate_output( $self, \%stimuli_hash )

Calculates and returns the `sum(weightage*input)` for each individual row of data. Actually, it justs add up all the existing weight since the `input` is always 1 for now :)

`%stimuli_hash` is the actual data to be used for training. It might contain useless columns.

This will get all the avaible dendrites using the `get_attributes` method and then use all the keys ie. headers to access the corresponding values.

This subroutine should be called in the procedural way for now.

## &_tune( $self, \%stimuli_hash, $tune_up_or_down )

Fine tunes the nerve. This will directly alter the attributes values in `$self` according to the attributes / dendrites specified in `new`.

The `%stimuli_hash` here is the same as the one in the `_calculate_output` method.

`%stimuli_hash` will be used to determine which dendrite in `$self` needs to be fine-tuned. As long as the value of any key in `%stimuli_hash` returns true (1) then that dendrite in `$self` will be tuned.

Tuning up or down depends on `$tune_up_or_down` specifed by the `train` method. The following constants can be used for `$tune_up_or_down`:

TUNE_UP

  Value is `1`

TUNE_DOWN

  Value is `0`

This subroutine should be called in the procedural way for now.

# VALIDATION RELATED METHODS

All the validation methods here have the same parameters as the actual `validate` method and they all do the same stuff. They are also used in the same way.

## take_mock_exam (...)

## take_lab_test (...)

## validate ( \%options )

This method validates the perceptron against another set of data after it has undergone the training process.

This method calculates the output of each row of data and write the result into the predicted column. The data begin written into the new file or the original file will maintain it's sequence.

Please take note that this method will load all the data of the validation stimuli, so please split your stimuli into multiple files if possible and call this method a few more times.

For `%options`, the followings are needed unless mentioned:

stimuli_validate => $csv_file

  This is the CSV file containing the validation data, make sure that it contains a column with the predicted values as it is needed in the next key mentioned: `predicted_column_index`

predicted_column_index => $column_number

  This is the index of the column that contains the predicted output values. `$index` starts from `0`.

  This column will be filled with binary numbers and the full new data will be saved to the file specified in the `results_write_to` key.

results_write_to => $new_csv_file

  Optional.

  The default behaviour will write the predicted output back into `stimuli_validate` ie the original data. The sequence of the data will be maintained.

*This method will call `_real_validate_or_test` to do the actual work.

# TESTING RELATED SUBROUTINES/METHODS

All the testing methods here have the same parameters as the actual `test` method and they all do the same stuff. They are also used in the same way.

## take_real_exam (...)

## work_in_real_world (...)

## test ( \%options )

This method is used to put the trained nerve to the test. You can think of it as deploying the nerve for the actual work or maybe putting the nerve into an empty brain and see how well the brain survives :)

This method works and behaves the same way as the `validate` method. See `validate` for the details.

*This method will call &_real_validate_or_test to do the actual work.

## _real_validate_or_test ( $data_hash_ref )

This is where the actual validation or testing takes place.

`$data_hash_ref` is the list of parameters passed into the `validate` or `test` methods.

This is a method, so use the OO way. This is one of the exceptions to the rules where private subroutines are treated as methods :)

## &_fill_predicted_values ( $self, $stimuli_validate, $predicted_index, $aoa )

This is where the filling in of the predicted values takes place. Take note that the parameters naming are the same as the ones used in the `validate` and `test` method.

This subroutine should be called in the procedural way.

# RESULTS RELATED SUBROUTINES/METHODS

This part is related to generating the confusion matrix.

## get_exam_results ( ... )

The parameters and usage are the same as `get_confusion_matrix`. See the next method.

## get_confusion_matrix ( \%options )

Returns the confusion matrix in the form of a hash. The hash will contain these keys: `true_positive`, `true_negative`, `false_positive`, `false_negative`, `accuracy`, `sensitivity`. More stats like `precision`, `specificity` and `F1_Score` can be obtain by setting the optional `more_stats` key to `1`.

If you are trying to manipulate the confusion matrix hash or something, take note that all the stats are in percentage (%) in decimal (if any) except the total entries.

For `%options`, the followings are needed unless mentioned:

full_data_file => $filled_test_file

  This is the CSV file filled with the predicted values.

  Make sure that you don't do anything to the actual and predicted output in this file after testing the nerve. These two columns must contain binary values only!

actual_output_header => $actual_column_name
predicted_output_header => $predicted_column_name

  The binary values are treated as follows:

  `0` is negative
  `1` is positive
more_stats => 1

  Optional.

  Setting it to `1` will process more stats that are usually not so important eg. `precision`, `specificity` and `F1_Score`

## &_collect_stats ( \%options )

Generates a hash of confusion matrix based on `%options` given in the `get_confusion_matrix` method.

## &_calculate_total_entries ( $c_matrix_ref )

Calculates and adds the data for the `total_entries` key in the confusion matrix hash.

## &_calculate_accuracy ( $c_matrix_ref )

Calculates and adds the data for the `accuracy` key in the confusion matrix hash.

## &_calculate_sensitivity ( $c_matrix_ref )

Calculates and adds the data for the `sensitivity` key in the confusion matrix hash.

## &_calculate_precision ( $c_matrix_ref )

Calculates and adds the data for the `precision` key in the confusion matrix hash.

## &_calculate_specificity ( $c_matrix_ref )

Calculates and adds the data for the `specificity` key in the confusion matrix hash.

## &_calculate_f1_score ( $c_matrix_ref )

Calculates and adds the data for the `F1_Score` key in the confusion matrix hash.

## &_calculate_negative_predicted_value( $c_matrix_ref )

Calculates and adds the data for the `negative_predicted_value` key in the confusion matrix hash.

## &_calculate_false_negative_rate( $c_matrix_ref )

Calculates and adds the data for the `false_negative_rate` key in the confusion matrix hash.

## &_calculate_false_positive_rate( $c_matrix_ref )

Calculates and adds the data for the `false_positive_rate` key in the confusion matrix hash.

## &_calculate_false_discovery_rate( $c_matrix_ref )

Calculates and adds the data for the `false_discovery_rate` key in the confusion matrix hash.

## &_calculate_false_omission_rate( $c_matrix_ref )

Calculates and adds the data for the `false_omission_rate` key in the confusion matrix hash.

## &_calculate_balanced_accuracy( $c_matrix_ref )

Calculates and adds the data for the `balanced_accuracy` key in the confusion matrix hash.

## display_exam_results ( ... )

The parameters are the same as `display_confusion_matrix`. See the next method.

## display_confusion_matrix ( \%confusion_matrix, \%labels )

Display the confusion matrix. If `%confusion_matrix` has `more_stats` elements, it will display them if they exists. The default elements ie `accuracy` and `sensitivity` must be present, while the rest can be absent.

`%confusion_matrix` is the same confusion matrix returned by the `get_confusion_matrix` method.

For `%labels`, since `0`'s and `1`'s won't make much sense as the output labels in most cases, therefore, the following keys must be specified:

zero_as => $category_zero_name
one_as => $category_one_name

Please take note that non-ascii characters ie. non-English alphabets might cause the output to go off :)

For the `%labels`, there is no need to enter "actual X", "predicted X" etc. It will be prefixed with `A:` for actual and `P:` for the predicted values by default.

## &_build_matrix ( $c_matrix, $labels )

Builds the matrix using `Text::Matrix` module.

`$c_matrix` and `$labels` are the same as the ones passed to `display_exam_results` and ``display_confusion_matrix.

Returns a list `( $matrix, $c_matrix )` which can directly be passed to `_print_extended_matrix`.

## &_print_extended_matrix ( $matrix, $c_matrix )

Extends and outputs the matrix on the screen.

`$matrix` and `$c_matrix` are the same as returned by `&_build_matrix`.

# NERVE DATA RELATED SUBROUTINES

This part is about saving the data of the nerve. These subroutines can be imported using the `:local_data` tag.

The subroutines are to be called in the procedural way. No checking is done currently.

See `PERCEPTRON DATA` and `KNOWN ISSUES` sections for more details on the subroutines in this section.

## preserve ( ... )

The parameters and usage are the same as `save_perceptron`. See the next subroutine.

## save_perceptron ( $nerve, $nerve_file )

Saves the `AI::Perceptron::Simple` object into a `Storable` file. There shouldn't be a need to call this method manually since after every training process this will be called automatically.

## revive (...)

The parameters and usage are the same as `load_perceptron`. See the next subroutine.

## load_perceptron ( $nerve_file_to_load )

Loads the data and turns it into a `AI::Perceptron::Simple` object as the return value.

# NERVE PORTABILITY RELATED SUBROUTINES

These subroutines can be imported using the `:portable_data` tag.

The file type currently supported is YAML. Please be careful with the data as you won't want the nerve data accidentally modified.

## preserve_as_yaml ( ... )

The parameters and usage are the same as `save_perceptron_yaml`. See the next subroutine.

## save_perceptron_yaml ( $nerve, $yaml_nerve_file )

Saves the `AI::Perceptron::Simple` object into a `YAML` file.

## revive_from_yaml (...)

The parameters and usage are the same as `load_perceptron`. See the next subroutine.

## load_perceptron_yaml ( $yaml_nerve_file )

Loads the YAML data and turns it into a `AI::Perceptron::Simple` object as the return value.

# TO DO

These are the to-do's that MIGHT be done in the future. Don't put too much hope in them please :)

- Clean up and refactor source codes

- Add more useful data for confusion matrix

- Implement shuffling data feature

- Implement fast/smart training feature

- Write a tutorial or something for this module

- and something yet to be known...

# KNOWN ISSUES

## Portability of Nerve Data

Take note that the `Storable` nerve data is not compatible across different versions.

If you really need to send the nerve data to different computers with different versions of `Storable` module, see the docs of the following subroutines:

- `&preserve_as_yaml` or `&save_perceptron_yaml` for storing data.

- `&revive_from_yaml` or `&load_perceptron_yaml` for retrieving the data.

# AUTHOR

Raphael Jong Jun Jie, `<ellednera at cpan.org>`

# BUGS

Please report any bugs or feature requests to `bug-ai-perceptron-simple at rt.cpan.org`, or through the web interface at https://rt.cpan.org/NoAuth/ReportBug.html?Queue=AI-Perceptron-Simple. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

# SUPPORT

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

        perldoc AI::Perceptron::Simple

You can also look for information at:

- RT: CPAN's request tracker (report bugs here)

  https://rt.cpan.org/NoAuth/Bugs.html?Dist=AI-Perceptron-Simple

- CPAN Ratings

  https://cpanratings.perl.org/d/AI-Perceptron-Simple

- Search CPAN

  https://metacpan.org/release/AI-Perceptron-Simple

# ACKNOWLEDGEMENTS

Besiyata d'shmaya, Wikipedia

# SEE ALSO

AI::Perceptron, Text::Matrix, YAML

# LICENSE AND COPYRIGHT

This software is Copyright (c) 2021 by Raphael Jong Jun Jie.

This is free software, licensed under:

      The Artistic License 2.0 (GPL Compatible)