2. float average=0;
3. float sum = 0;
4. float[] storedValues;
5. int count = 0;
6. 
   
7. float quickanddirty = 0;
8. 
   
9. 
   
10. void setup()
11. {
12.   storedValues = new float[10];
13. }
14. 
    
15. void draw()
16. {
17.   float newValueFromStream = random(1.0);
18.   
19.   AddNewValue(newValueFromStream);
20.   
21.   float ave = 0;
22.   
23.   if(count > 0)
24.   {
25.     ave = sum / count;
26.   }
27.   
28.  
29.   
30.   //or like this 
31.   
32.   float lerp = 0.95; //must be between 0-1
33.   quickanddirty = lerp * quickanddirty + (1.0-lerp) * newValueFromStream;
34.   
35.   
36.    println("count: " + count + " new value: " +newValueFromStream + " proper average: " + ave + " quick and dirty: " + quickanddirty);
37. }
38. 
    
39. 
    
40. 
    
41. void AddNewValue(float val)
42. {
43.   if(count < storedValues.length)
44.   {
45.     //array is not full yet
46.     storedValues[count++] = val;
47.     
48.     sum += val; 
49.   }
50.   else
51.   {
52.     sum += val; 
53.     sum -= storedValues[0];
54.     
55.     //shift all of the values, drop the first one (oldest) 
56.     for(int i = 0; i < storedValues.length-1; i++)
57.     {
58.       storedValues[i] = storedValues[i+1] ;
59.     }
60.     //the add the new one
61.     storedValues[storedValues.length-1] = val;
62.   }
63. }

1.   total -= data[p];
2.   data[p] = value;
3.   total += value;
4.   p = ++p % data.length;
5.   if(n < data.length) n++;
6.   average = total / n;

circular buffer  yes nice.