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Thread: finding average in 2d arrays
 02242011, 01:15 AM #1Member
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finding average in 2d arrays
im trying to find the average of the high temprature and return it..
Java Code:import java.util.*; public class Chap9Ex12p589 { static Scanner console = new Scanner(System.in); public static void main(String[] args) { int[][] temperature = {{50,16},{47,2},{65,35},{68,41},{73,50}, {81,66},{93,73},{101,82},{90,75}, {75,60},{67,53},{56,38}}; printTemp(temperature); avgHighTemp(temperature); }//end main //method public static void printTemp(int[][] temp) { for (int high = 0; high < temp.length; high++) { for (int low = 0; low < temp[high].length; low++) System.out.printf("%7d", temp[high][low]); System.out.println(); } } public static int avgHighTemp(int[][] temp) { int sum =0; double avg= 0; for (int high = 0; high < temp[0].length; high++) { sum = 0; for (int low = 0; low < temp.length; low++) sum += temp[high][low]; } avg = sum / temp.length System.out.println("The average of the high temperature is " + String.format("%.2f", avg)); return avg; } }//end class
 02242011, 01:23 AM #2Senior Member
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Great stuff, and your question/problem is?
 02242011, 01:50 AM #3Member
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in this method im trying to find the average of the high temperature. i compile it and getting an error
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 2
at Chap9Ex12p589.avgHighTemp(Chap9Ex12p589.java:43)
at Chap9Ex12p589.main(Chap9Ex12p589.java:18)
Java Code:public static int avgHighTemp(int[][] temp) { int sum =0; double avg= 0; for (int high = 0; high < temp[0].length; high++) { sum = 0; for (int low = 0; low < temp.length; low++) sum += temp[high][low]; [U]//this might be where my problem is[/U] } avg = sum / temp.length System.out.println("The average of the high temperature is " + avg); return avg; }
 02242011, 02:02 AM #4Senior Member
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That certainly is a problem, not your only one though. How many columns does your 2d array have? Why are you getting a number 2 with the ArrayOutOfBounds exception?. Try to answer these questions.
Java Code:int[][] temperature = {{50,16},{47,2},{65,35},{68,41},{73,50}, {81,66},{93,73},{101,82},{90,75},{75,60},{67,53},{56,38}};
Java Code:for (int high = 0; high < temp[0].length; high++) { sum = 0; for (int low = 0;[COLOR="DarkOrange"] low < temp.length[/COLOR]; low++) sum += temp[high][low]; //this might be where my problem is }
 02242011, 02:11 AM #5Member
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there is one inside the main and the avghightemp method.
i have 12 rows and 2 columns. first column is the high temp and the second is low temp...
 02242011, 02:13 AM #6Senior Member
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What value is temp.length?
 02242011, 02:15 AM #7
 02242011, 02:16 AM #8Member
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i changed that to 12 :) i forgot to changed it when i posted it.
 02242011, 02:47 AM #9
Changed what to 12? Did you solve your problem?
 02242011, 03:32 AM #10Member
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[code]
public static int avgHighTemp(int[][] temp)
{
int sum;
int avg= 0;
for (int col = 0; col < temp[0].length; col++)
{
sum = 0;
for (int row = 0; row < temp.length; row++)
sum += temp[row][col];
avg = sum / temp.length;
}
return avg;
}
[\code]
thanks for the help al_Marshy_1981 and junky
 02242011, 03:33 AM #11Senior Member
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That method will not give you an average
 02242011, 03:45 AM #12Member
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it didn't give me a right num :)
 02242011, 03:53 AM #13
So work out why it doesn't. Try adding a bunch of print statements at various points so you can see what values your variables have. Hopefully one (or more) of them will jump out at you and you say "Why is it X when it should be Y?"
 02242011, 04:03 AM #14Member
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i printed out my sum and it prints both of sum of my columns.. the avg pickin up the last sum which is my low temp(2nd col) instead the first col that was why i have the wrong avg..
thanks.. ill work on it
 02242011, 04:14 AM #15Member
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Java Code:public static int avgHighTemp(int[][] temp) { int sum = 0; int avg= 0; for (int col = 0; col < temp[0].length; col++) { sum = 0; for (int row = 0; row < temp.length; row++) sum += temp[row][0]; System.out.println(sum); } avg = sum / temp.length; return avg; }
Java Code:50 16 47 2 65 35 68 41 73 50 81 66 93 73 101 82 90 75 75 60 67 53 56 38 866 866 [U]//IT WAS 587 THE SUM OF MY 2ND COLUMN[/U] The average of the high temperature is 72
Java Code:sum += temp[row][0];
thankz :)
 02242011, 04:20 AM #16Senior Member
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Because highest temperatures were stored in column 1 of your array, but array access starts its count from 0. So 0 = column 1. The way you accessed the array was unconventional though.
 02242011, 04:21 AM #17Java Code:
sum += temp[row][0];
Oops!
Misunderstood. I thought you were trying to average all the temperatures. If all you want is the high temps in the left column then you don't need nested loops. A single loop is all you need.
 02242011, 04:31 AM #18Member
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@al: thanks and how can i make it simple?
@junky: it did give me the right answer and all i need to sum up is the first col
my code is not that professional... that is why im here for additional lecture :)
 02242011, 04:32 AM #19Member
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