How to calculate Weighted Average

[tac24]

After the base search such as:

......
 | stats sum(r1) as t_r1  sum(r2) as t_r2  sum(duras) as total_dura c(member) as samples by group 
 | eval ratio1 = t_r1/total_dura
 | eval ratio2 = t_r2/total_dura
 | table group ratio1 ratio2 samples 

I got the table like below:

   group        ratio1           ratio2        samples
---------------------------------------------------------------
     A            0.8              0.2            100
     B            0.3              0.7             50
     C            0.5              0.5            300

Then, I can calculate simple average over group by: | stats avg(ratio1) avg(ratio2) .
Could someone help me how to calculate weighted average by using samples?
i.e., the weight for A is 100/(100+50+300), B is 50/(100+50+300),...

[tac24]

Thank you very much, it worked!
Excuse me, my question is rather ambiguous. I would like to add something for beginners like me...
To get weighted-average finally, after eventstats, the following commands can be added.

 | eval w_avg_of_ratio1_per_group = ratio1*samples/total 
 | stats sum(w_avg_of_ratio1_per_group) as w_avg_of_ratio1

[renjith_nair · Accepted solution]

You can use eventstats to achieve this

|eventstats sum(samples) as total | eval weighted_avg=samples/total 

You can use by clause in eventstats to group the records