Recalculate an average value

问题

In my Java application I need to recalculate an average value based on the following data:

1. I know current avg value - avgValue
2. I know that avgValue is an average value for list of 12 values - count.

Based on this information how to recalculate avgValue when a new value is added to this list of previous 12 values. What is the new avgValue for list of 13 values - count + 1 ?

回答1:

Current Sum = avgValue * 12
New sum = current Sum + New value
New average = New sum / 13

回答2:

If you want to make sure you don't overflow your data type then you will want to avoid computing the sum. I would suggest using:

New average = avgValue + ((New value - avgValue) / 13)

来源：https://stackoverflow.com/questions/31904332/recalculate-an-average-value