[Qgis-user] quantile calculation

[matteo]

Hi guys,
a simple question: in the graduated classification method, one can 
choose several methods to classify the data (natural breaks, 
quantile...) and also the class numbers.
If I choose the quantile method, how can I know the interval limit of 
each range? I mean, if the data are classified in 5 classes, I think 
that the first class goes from 0 to the 20th quantile, the second class 
from the 20th to the 40th and so on.

But can I set that the first class should go from 0 to the 25th 
percentile, the second from the 25th to the 50th...

In other word, can I choose the quantile limits?

Thanks in advance

Cheers

Matteo