Question

Right now, I’m trying to create an algorithm that gives a score to a user, depending on his input in a text field.

This score is supposed to encourage the user to add more text to his personal profile.

The way the algorithm should work, is that it should account a certain weight to the first word, and a little less weight to the second word. The third word will receive a little less weight than the second word, and so on.

The goal is to encourage users to expand their texts, but to avoid spam in general as well. For instance, the added value of the 500th word shouldn’t be much at all.
The difference between a text of 100 words and a text of 500 words should be substantial.

Am I making any sense so far?

Right now, I wouldn’t know where to begin with this question. I’ve tried multiple Google queries, but didn’t seem to find anything of the sort. Can anyone point me in the right direction?
I suppose such an algorithm must already exist somewhere (or at least the general idea probably exists) but I can’t seem to be able to find some help on the subject.

Can anyone point me in the right direction?
I’d really appreciate any help you can give me.

Thanks a lot.

Answer 1

// word count in user description
double word_count = ...; 

// word limit over which words do not improve score
double word_limit = ...;

// use it to change score progression curve
// if factor = 1, progression is linear
// if factor < 1, progression is steeper at the beginning
// if factor > 1, progression is steeper at the end
double factor = ...;


double score = pow(min(word_count, word_limit) / word_limit, factor);