Getting "nan" in my verbose output

[David Relson]

On Thu, 8 Apr 2004 11:17:36 -0700
Chris Wilkes wrote:

> Hi all,
> 
>   I just upgraded to version 0.17.5 and am looking at one of my user's
> "makespam" folders where they dump email to be classified as spam.
>   What's odd is that the spam values of the emails were all around 0.5
> until I ran them through a "-Ns" and then suddenly the spam count was
> 0! Digging deeper I found the problem : my -Ns reduced the total good
> count to 0.
> 
> Looking at one particular message I found the word "Pharmacy" in it.
>   
>   $ bogofilter -vvv -I bademail.txt | grep -i Pharmacy
>    Word            n    pgood      pbad    fw  U
>   "Pharmacy"      86      nan  0.002943   nan  -
>   $ bogoutil -w ./wordlist.db Pharmacy
>                   spam   good
>      Pharmacy       86      0
>   $ bogoutil -w ./wordlist.db .MSG_COUNT
>                   spam   good
>     .MSG_COUNT   29226      0
> 
> What gives?  This word has only been seen in spams (86 to 0) yet it
> doesn't contribute to the spam count ("-" for U).

Chris,

Did you do a whole bunch of "-Ns" to cause the zero???  Do you think the
good count went to zero appropriately, or inappropriately?

As you've discovered the "nan" is a result of a zero message count.
Bogofilter uses the message count as a divisor and the division by zero
causes the problem.  As a minor speedup, the "if 0, use 1 for division"
check was deleted a while ago.  I'll modify the code and fix the code to
fix this for the next release.

David