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javaarrays
Austin Smith
Austin Smith

Reputation: 19

Java - Finding the average of an array while excluding a particular value.

I am trying to calculate and return the average of an array of integer values. The problem is, the array I am calculating the average from has values I need to find the average of, and values I need to exclude.

For example, take this as being my data set in the array. 20, -999, -10, 50, -999, 40, 30

I need to find the average but exclude any -999 value from the calculation.

How can I go about removing the -999 value from my sums and then find the new value to divide by at the end? Is there a way to keep count of the values I exclude? How can I exclude a value and move on to the next? 

    public static double averageTemperature(int[] temperatures)
{   
    double sum = 0.0;
    double avg = 0.0;
    for (int i =0; i < temperatures.length; i++)
    {
      if (i == -999)
      {
      // what technique is there to exlude and keep counting?                   
      }
      else
      {
      sum += i;
      }
    }

    avg = sum / temperatures.length;
    return avg;
}

Upvotes: 0

Views: 1170

Answers (4)

Jacob G.
Jacob G.

Reputation: 29710

The easiest way to compute the average while filtering out any unwanted values would be:

double average = Arrays.stream(temperatures)
                       .filter(i -> i != -999)
                       .average();

Upvotes: 0

Rajith Pemabandu
Rajith Pemabandu

Reputation: 614

suppose you are correct with the logic but you are not getting the sum of the temperature values.

public static double averageTemperature(int[] temperatures)
     {   
         double sum = 0.0;
         double avg = 0.0;
         for (int i =0; i < temperatures.length; i++)
         {
           if (temperatures[i] == -999)
           {
               continue;
           }
           else
           {
           sum += temperatures[i];
           }
         }

         avg = sum / temperatures.length;
         return avg;
     }

hope this is what you are looking for.

Upvotes: 0

user7391763
user7391763

Reputation:

Using Java 8 you can do;

temperatures = Arrays.stream(temperatures).filter(x -> x != -999).toArray();

You can exclude any array value this way using predicate statements.

Calculating the mean is as simple as just looping the array and dividing by the length then.

 float mean;
 for (int i = 0; i < temperatures.length; ++i) {
     mean += (float) temperatures[i];
 }
 mean /= (float) temperatures.length;

Note to use a float for the mean and cast your integer array values to float also to avoid integer division, as well as the length of the array.

Upvotes: 2

mlimper
mlimper

Reputation: 5250

This should be pretty straightforward - just use a variable as counter for the "valid" entries. You also need to access the values in the array properly. Here's a proposal (untested), which assumes "valid" entries are those not equal t0 -999 (modify the condition as you like):

public static double averageTemperature(int[] temperatures)
{   
    double sum = 0.0;
    double avg = 0.0;
    int validEntries = 0;
    for (int i =0; i < temperatures.length; i++)
    {
        // process only "valid" entries
        if (temperatures[i] != -999)
        {
            sum += temperatures[i];
            ++validEntries;
        }
    }
    avg = sum / validEntries;
    return avg;
}

Upvotes: 3

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