Maciej Gawinecki wrote:
> Two questions related to the topic

WTF has this got to do with SGML or XML?

///Peter

[Followups reset]

> 1. If I have an empty set of relevant results, then it would be 
> better to have no answers from the system at all. But neither
> precision nor recall gives penalties for returning false positives in
> this case (0/1=0/2=...=0/100). How people handle with this ? Is there
> other measure for this cases ?
> 
> 2. Let say I have ranking:
> 
>     1. A
>     2. B *
>     3. C
>     4. D *
>     5. F
> 
> Where relevant answers are: B,D,E, and relevant answers found by the 
> system are marked with a star (*).
> 
>    Then for recall level 1/3 I have precision 1/2,
>    for recall level 2/3 I have precision 2/4=1/2.
> 
> The last position of ranking, false positive, is not counted in the 
> precision/recall measure, as in this measure "only positions where an
> increase in recall is produced". I have the system which returns 
> some false positives at the end of ranking, but how can I measure/ 
> compare it with other systems in terms of effectiveness, if
> precision/ recall does not take it into account ?
> 
> TIA,
> Maciej