There is a picklist field Prod Type in child object ,sub opportunity . Based on similar Prod Type values the child object sub opportunity's field "revenue" should get averaged and for differnt product types values the child object "Sub opportunity " revenue field should be sumed at the parent object that is opportunity.
Please help me to achive this in my trigger 

trigger RolllupSubAmt  on Sub_Opportunity__c ( after insert, after update,after delete,after undelete) {
     Set<Id> oppIdSet=new Set<Id>();
     List<Opportunity> opptyListToUpdate=new List<Opportunity>();
     if(Trigger.isInsert || Trigger.isUpdate || Trigger.isUndelete){
          for(Sub_Opportunity__c subopp : Trigger.new){
             if(subopp.Opportunity__c!= null){
                oppIdSet.add(subopp.Opportunity__c);
             }      
          }
     }
     If(Trigger.isDelete){
       for(Sub_Opportunity__c opp : Trigger.old){
            if(opp.Opportunity__c!= null){
               oppIdSet.add(opp.Opportunity__c); 
            }       
        }
      }
     for(AggregateResult res : [SELECT Opportunity__c,avg(Actual_Revenue_Rollup__c)can FROM Sub_Opportunity__c WHERE Opportunity__c IN :oppIdSet GROUP BY  Opportunity__c ]) {
        opptyListToUpdate.add(new Opportunity(Id=(Id)res.get('Opportunity__c'), Actual_Revenue2__c=(Double)res.get('can')));
    }
    try{
        update opptyListToUpdate;
     }catch(DmlException de){
        System.debug(de);
     }
}