fp-fn-to-tcr   [plain text]

#!/usr/bin/perl
#
# <@LICENSE>
# Copyright 2004 Apache Software Foundation
# 
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# 
#     http://www.apache.org/licenses/LICENSE-2.0
# 
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# </@LICENSE>

use Getopt::Long;
use vars qw($opt_lambda $opt_fn $opt_fp $opt_spam $opt_ham);
GetOptions("lambda=f", "fn=f", "fp=f", "spam=f", "ham=f");

# lambda value for TCR equation, representing the cost of of an FP vs. the
# cost of a FN.  Some example values are: 1 = tagged only, 9 = mailed back
# to sender asking for token, 999 = blocking or deleting a message.
#
# We roughly aim for a value representing "moved to infrequently-read folder".

my $lambda = 50; if ($opt_lambda) { $lambda = $opt_lambda; }

if (!$opt_spam && !$opt_ham) {
  die "usage: fn-fp-to-tcr [-lambda l] -fn n -fp n -spam n -ham n\n\n";
}

# convert to the TCR metrics used in the published lit
my $nspamspam = $opt_spam;
my $nspamlegit = $opt_fn;
my $nlegitspam = $opt_fp;
my $nlegitlegit = $opt_ham;
my $nlegit = $opt_ham + $opt_fp;
my $nspam = $opt_spam + $opt_fn;

my $werr = ($lambda * $nlegitspam + $nspamlegit)
                / ($lambda * $nlegit + $nspam);

my $werr_base = $nspam
                / ($lambda * $nlegit + $nspam);

$werr ||= 0.000001;     # avoid / by 0
my $tcr = $werr_base / $werr;

my $sr = ($nspamspam / $nspam) * 100.0;
my $sp = ($nspamspam / ($nspamspam + $nlegitspam)) * 100.0;

printf "TCR(l=%d): %3.6f\nSpamRecall: %3.6f%%\nSpamPrecision: %3.6f%%\n",
    $lambda, $tcr, $sr, $sp;