bayesol - a Bayes solution calculator for use with dbacl.

**bayesol**
[-DVNniv] -c *riskspec* [FILE]...

**bayesol**
-V

**bayesol** is a Bayes solution calculator designed to combine the output of

**dbacl**(1) with a prior distribution and a risk specification, and
calculate the optimal Bayesian decision (which minimizes the posterior risk).

The risk specification is read from the text file

*riskspec* and must be
written in a simple format described below. The

**dbacl**(1) output can
either be read from FILE or from STDIN.

On success,

**bayesol** returns a positive integer corresponding to the
category with the lowest risk. In case of a problem,

**bayesol** returns
zero.

- -c
- Classify using
*riskspec*. See the section RISK
SPECIFICATION.

- -i
- Fully internationalized mode. Forces the use of wide
characters internally, which is necessary in some locales. This incurs a
noticeable performance penalty.

- -n
- Print risk scores for each
*category*. Each score is
(approximately) the logarithm of the expected risk under that category.
The lowest score (ie closest to -infinity) is best, etc.

- -N
- Print recursive risk scores for each
*category*. Each
score is (approximately) the logarithm of the best score based on the
remaining categories, after the previously best scoring categories have
been removed, and a normalizing factor was added. A full description is
given in the technical report listed at the end of this manpange. The
largest score (ie closest to +infinity) is best, etc.

- -v
- Verbose mode. Prints to STDOUT the category with minimum
posterior risk. In case several categories are possible, prints the first
category in the order in which they appear in the categories section of
*riskpspec*.

- -D
- Print debug output. Do not use.

- -V
- Print the program version number and exit.

**bayesol** needs to read a text file

*riskspec* containing a risk
specification. The format of this text file is as follows

- categories {
*cat1*, *cat2*,...,
*catN*}

prior { *p1*, *p2*,..., *pN*}

loss_matrix {

" *regex1*" *c1* [ *formula11*,
*formula12*,..., *formula1N*]

" *regex2*" *c2* [ *formula21*,
*formula22*,..., *formula2N*]

.

.

" *regexM*" *cM* [ *formulaM1*,
*formulaM2*,..., *formulaMN*]

}

In the above,

*cat1*,

*cat2*,

...,

*catN*, are category
names,

*p1*,

*p2*,

...,

*pN*, are non-negative numbers,

*regex1*,

*regex2*,

...,

*regexM*, are (possibly empty)
regular expression strings,

*c1*,

*c2*,

...,

*cM*, are
instances of the category names

*cat1*,

*cat2*,

...,

*catN*, and the formulas are numbers or mathematical expressions.

Every category which appears in the categories section must appear at least once
in the loss_matrix section, with an empty "" regular expression. To
construct the actual loss matrix used in the decision calculations,

**bayesol** selects, for each category appearing in the categories section,
the first row whose regular expression is matched within FILE or STDIN, or the
first row with empty regular expression if there are no matches.

Each formula can be either a single number, or an algebraic combination of the
operators exp(), log(), +, -, *, /, ^ and parentheses (). The string
"inf" is parsed as the value infinity. Also, the string
"complexity" is recognized, and converted to the complexity for that
category as reported by

**dbacl**(1). Finally, if the corresponding regular
expression contains submatches delimited by parentheses, their numerical
values can be used inside the formulas as the special variables $1, ..., $9.
Note that submatches which aren't numerical are converted to the value zero.

Case is important. Spaces and newlines can be liberally inserted. Comments must
start with a # and extend to the end of the line.

Typically,

**bayesol** is used together with

**dbacl**(1). An invocation
looks like this:

% dbacl -c one -c two -c three sample.txt -vna | bayesol -c toy.risk -v

See /usr/share/doc/dbacl/costs.ps for a description of the algorithm used. See
also /usr/share/doc/dbacl/tutorial.html for a more detailed overview.

The source code for the latest version of this program is available at the
following locations:

http://www.lbreyer.com/gpl.html

http://dbacl.sourceforge.net

Laird A. Breyer <laird@lbreyer.com>

**dbacl**(1),

**mailcross**(1),

**mailfoot**(1),

**mailinspect**(1),

**mailtoe**(1),

**regex**(7)