NAME
Lucy::Analysis::SnowballStopFilter - Suppress a “stoplist” of common words.
SYNOPSIS
my $stopfilter = Lucy::Analysis::SnowballStopFilter->new(
language => 'fr',
);
my $polyanalyzer = Lucy::Analysis::PolyAnalyzer->new(
analyzers => [ $tokenizer, $normalizer, $stopfilter, $stemmer ],
);DESCRIPTION
A “stoplist” is collection of “stopwords”: words which are common enough to be of little value when determining search results. For example, so many documents in English contain “the”, “if”, and “maybe” that it may improve both performance and relevance to block them.
Before filtering stopwords:
("i", "am", "the", "walrus")After filtering stopwords:
("walrus")SnowballStopFilter provides default stoplists for several languages, courtesy of the Snowball project, or you may supply your own.
|-----------------------|
| ISO CODE | LANGUAGE |
|-----------------------|
| da | Danish |
| de | German |
| en | English |
| es | Spanish |
| fi | Finnish |
| fr | French |
| hu | Hungarian |
| it | Italian |
| nl | Dutch |
| no | Norwegian |
| pt | Portuguese |
| sv | Swedish |
| ru | Russian |
|-----------------------|CONSTRUCTORS
new
my $stopfilter = Lucy::Analysis::SnowballStopFilter->new(
language => 'de',
);
# or...
my $stopfilter = Lucy::Analysis::SnowballStopFilter->new(
stoplist => \%stoplist,
);Create a new SnowballStopFilter.
stoplist - A hash with stopwords as the keys.
language - The ISO code for a supported language.
METHODS
transform
my $inversion = $snowball_stop_filter->transform($inversion);Take a single Inversion as input and returns an Inversion, either the same one (presumably transformed in some way), or a new one.
inversion - An inversion.
INHERITANCE
Lucy::Analysis::SnowballStopFilter isa Lucy::Analysis::Analyzer isa Clownfish::Obj.