Averaging Values

Using Arduino Sensors
1

Hello,
First, I'm such a newbie! Second, I am working with 5 photocells which are connected to the arduino from A0 -A4. I am able to read the values and such. However, I have to average the top three values of the photocells.

For example:
Cell 1 = 100
Cell 2 = 600
Cell 3 = 200
Cell 4=300
Cell 5 = 500

I have to get the average of the top three, so 600+300+500. I am trying to put them in an array and sort the top three and get the average like that, however, I am having issues.

code that I have so far:

int analogPin0 = 0; 
    int analogPin1 = 1; 
    int analogPin2 = 2; 
    int analogPin3 = 3; 
    int analogPin4 = 4; 
   int number;
    
  
    int analogreading = 0;
    int analogreading1 = 1;
    int analogreading2 = 2;
    int analogreading3 = 3;
    int analogreading4 = 4;
    
    int list[] = { analogPin0, analogPin1, analogPin2, analogPin3, analogPin4 };

    void setup()
    {
      Serial.begin(9600);  
    }

    void loop()
    {
   analogreading = analogRead(analogPin0);
   Serial.print("Pin0=" );
  
        Serial.println(analogreading);
       
    
 analogreading1=   analogRead(analogPin1);
       Serial.print("Pin1 =");
        Serial.println(analogreading1);
        
         analogreading2=   analogRead(analogPin2);
       Serial.print("Pin2 =");
        Serial.println(analogreading2);
        
        
          analogreading3=   analogRead(analogPin3);
       Serial.print("Pin3 =");
        Serial.println(analogreading3);

        analogreading4=   analogRead(analogPin4);
       Serial.print("Pin4 =");
        Serial.println(analogreading4);
        
     //   number=(analogreading1 + analogreading2)/2;
     //   Serial.print("num=");
     //   Serial.println(number);
        
   
        for (int i=3 ; i ; i--) {
        for (int j=0 ; (j + i) < 5 ; j++) {
            if (list[ j ] < list[ j + i ]) {
                int t = list[ j ];
                list[ j ] = list[ j + i ];
                list[ j + i ] = t;
            }
        }
    }
    int sum = 0;
    for (int k=0 ; k < 3 ; k++) {
        sum += list[ k ];
    }
    float average = sum / 3.0;
    
    Serial.print("avg=");
    Serial.println(average);
    
    
       
        delay(2000);
     
    }

And the output is just:

Pin0=157
Pin1 =173
Pin2 =170
Pin3 =142
Pin4 =175
avg=3.00

Pin0=157
Pin1 =172
Pin2 =169
Pin3 =140
Pin4 =173
avg=3.00

The Average is remaining the same?

in the list the average should be 173 for the first one and 171 for the second?

Thank you so much for helping.

2

The loop with 'i' and 'j', is that a sorting algorithm ?
Where did you get that from ? Can you print the 5 values after sorting ?

3

It is supposed to be a sorting algorithm, However I don't think its doing its job, the output that I have posted under the code is what I am getting. of course the photocell numbers are different.

4

You are initializing list[] to contain the numbers 1,2,3 and 4 and those are never changed.
Why do you think you need to sort the list?

5

Try the following: actually should order any number of integers.
int readings[5];
int rank[5];
int i, j;

//first, put all the readings in the readings[] array, any order

for (i = 0; i < 5; i++) rank = 0; //initialize the rank array

  • for (i = 0; i < 5; i++)*
  • for(j = i+1; j < 5; j++)*
    if readings[j] <= readings rank ++;
    I didn't test this, but I'm pretty sure it will work. Good luck.
    John Doner
    When this is done running, the rank[] array should contain the digits 0, 1, 2, 3, 4 in some order, and the location of the value 4 in rank[] should correspondto the location of the largest reading in readings[], etc.
6

I didn't test this, but I'm pretty sure it will work. Good luck.

That code will never even compile.

7

a starter slightly different

//
//    FILE: sevenofnine.ino
//  AUTHOR: Rob Tillaart
// VERSION: 0.1.00
// PURPOSE: 
//    DATE: 
//     URL:
//
// Released to the public domain
//
int ar[] = { 
  157, 173, 170, 0, 175, 142, 165, 181, 49 };

void setup() 
{
  Serial.begin(115200);
  Serial.println("Start ");

  bubblesort(ar, 9);
  int sum = 0;
  for (int i = 2; i < 9; i++)
  {
    sum += ar[i];
  }
  float avg = sum/7.0;
  Serial.println(avg, 3);
}

void loop() 
{
}

void bubblesort(int in[], int len) 
{
  int tmp;
  for (int j = 0; j < len; j++) 
  {
    for (int i = 1; i < len - j; i++) 
    {
      if(in[i-1] > in[i])
      {
        tmp = in[i];
        in[i] = in[i-1];
        in[i-1] = tmp;
      }
    }
  }
}