NAME

DSP::LinPred - Linear Prediction

SYNOPSIS

            

              
              
use DSP::LinPred;
# OPTIONS
# mu       : Step size of filter. (default = 0.001)
#
# h_length : Filter size. (default = 100)
# dc_mode  : Direct Current Component estimation.
#            it challenges to estimating DC component when set 1.
#            (default = 1 enable)
# dc_init  : Initial DC bias.
#            It *SHOULD* be set value *ACCURATELY* when dc_mode => 0.
#            (default = 0)
#
# stddev_mode : Step size correction by stddev of input.
#               (default = 1 enable)
# stddev_init : Initial value of stddev.
#               (default = 1)
#
my $lp = DSP::LinPred->new;
# set filter
$lp->set_filter({
                 mu => 0.001,
                 filter_length => 500,
                 dc_mode => 1,
                 stddev_mode => 1
                });
# defining signal x
my $x = [0,0.1,0.5, ... ]; # input signal
# Updating Filter
$lp->update($x);
my $current_error = $lp->current_error; # get error
# Prediction
my $pred_length = 10;
my $pred = $lp->predict($pred_length);
for( 0 .. $#$pred ){ print $pred->[$_], "\n"; }
            
          

DESCRIPTION

DSP::LinPred is Linear Prediction by Least Mean Squared Algorithm.

This Linear Predicting method can estimate the standard deviation, direct current component, and predict future value of input.

METHODS

set_filter

set_filter method sets filter specifications to DSP::LinPred object.

            

              
              
$lp->set_filter(
    {
        mu => $step_size, # <Num>
        filter_length => $filter_length, # <Int>
        dc_init => $initial_dc_bias, # <Num>
        dc_mode => $dc_estimation, # <Int>, enable when 1
        stddev_init => $initial_stddev, # <Num>
        stddev_mode => $stddev_estimation # <Int>, enable when 1
    });
            
          

update

update method updates filter state by source inputs are typed ArrayRef[Num].

            

              
              
my $x = [0.13,0.3,-0.2,0.5,-0.07];
$lp->update($x);
            
          

If you would like to extract the filter state, you can access member variable directly like below.

            

              
              
my $filter = $lp->h;
for( 0 .. $#$filter ){ print $filter->[$_], "\n"; }
            
          

predict

predict method generates predicted future values of inputs by filter.

            

              
              
my $predicted = $lp->predict(7);
for( 0 .. $#$predicted ){ print $predicted->[$_], "\n";}
            
          

filter_dc

This method can calculate mean value of current filter.

            

              
              
my $filter_dc = $lp->filter_dc;
            
          

filter_stddev

This method can calculate standard deviation of current filter.

            

              
              
my $filter_stddev = $lp->filter_stddev;
            
          

READING STATES

current_error

            

              
              
# It returns value of current prediction error
# error = Actual - Predicted
my $current_error = $lp->current_error;
print 'Current Error : '.$current_error, "\n";
            
          

h

            

              
              
# It returns filter state(ArrayRef)
my $filter = $lp->h;
print "Filter state\n";
for( 0 .. $#$filter ){ print $_.' : '.$filter->[$_],"\n"; }
            
          

x_count

            

              
              
# It returns value of input counter used in filter updating.
my $x_count = $lp->x_count;
print 'Input count : '.$x_count, "\n";
            
          

dc

            

              
              
# Get value of current Direct Current Components of inputs.
my $dc = $lp->dc;
print 'Current DC-Component : '.$dc, "\n";
            
          

stddev

            

              
              
# Get value of current standard deviation of inputs.
my $stddev = $lp->dc;
print 'Current STDDEV : '.$stddev, "\n";
            
          

EXPERIMENTAL OPTIONS

iir_mode and iir_a

In set_filter option. if set iir_mode to 1, and iir_a, it challenges to calculate DC value and stddev by using IIR filter.

IIR spec: next_dc = (current_input - iir_a * current_dc) / (1 - iir_a)

next_stddev = (abs(current_input - current_dc) - iir_a * current_stddev) / (1 - iir_a)

            

              
              
# set_filter with iir_mode on.
$lp->set_filter({
                 mu => 0.001,
                 filter_length => 500,
                 dc_mode => 1,
                 stddev_mode => 1,
                 iir_mode => 1,
                 iir_a => 0.01
                });
            
          

LICENSE

Copyright (C) Toshiaki Yokoda.

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

AUTHOR

Toshiaki Yokoda <>

cpanm DSP::LinPred

perl -MCPAN -e shell
install DSP::LinPred