[flabbergaster]

I can't translate this to straightforward arithmetic

[ghostwalker]

Could we have some context/background.

[flabbergaster]

I got this formula from a paper. Here is the snippet.



What I understood of it is that the first rank in each result set will have a score of 1, and the lowest will have a score of 0.

Rank and num_of_retrived_docs can be anything numerically valued? There are lots of ranks and one num_of_retrived docs?

Not sure what else? Thanks.

[ghostwalker]

I partially agree.

The hightest rank_sim will be 1, but the lowest won't quite reach zero.

Using their example for retrieving the top-ranked 1000 documents.

Then your formula becomes:

So if your document is ranked number 1 out of 1000, the Rank_Sim value is



And if it is ranked 10, as per the example, then the Rank_Sim value is



The overall effect of the Rank_Sim function is, given n top ranked documents, then to scale the ranking so that instead of running from 1 up to n, it runs from 1 down to 1/n, linearly.

Edit: See attached for a plot of Rank_Sim against rank, for n=100

[flabbergaster]

Sorry I still don't understand.

My maths is awful.

I'm trying to figure out how to convert that into something I can work out on the computer with basic arithmetic operators.

Do I want to use brackets for the divide by bit?

Many thanks.

[flabbergaster]

Thanks just got it!