[RESOLVED] arrays -- multidimensional confusion

[robkir]

I am stopped on this one--I understand an array when it has one element ($team1[$i]), but two or more elements confounds me.

Here's what I want to do.

Teams can either win, tie or lose a game. Over ten games they might have 5 wins, 3 ties and 2 loses. So the array's contents after processing would look like this:

$team1[5][3][2]

I can't figure out, even after reading dozens of websites, how I increment wins, ties, and loses. If I was tracking one element I'd use the +=. As the routine loops through all the games played in a season, it increments only one of the three elements per game since a team can only win or tie or lose.

Could somebody point me in the right direction? And would I extract the data from the array using foreach?

The following code shows the structure I use to gather the info. It is not keeping track of wins, ties or loses, it is merely adding up all the team's points (3 points for a win, one point for a tie and zero points for a loss).

//team1 is home team and team2 is away team
      if($score1 > $score2)
      { 
      $whichTeam= $team1;  

      $teamName[$whichTeam]+=3 ;

// Tie Game      

      }
        elseif ($score1 == $score2) 
      {    

        $whichTeam= $team1;  

        $teamName[$whichTeam]+=1 ;

    $whichTeam= $team2;  
    $teamName[$whichTeam]+=1 ;   
    $ties[$whichTeam]+=1;

//Who was the winner, team two        

      }
        elseif($score1 < $score2)
      {       

        $whichTeam = $team2;
        $teamName[$whichTeam]+=3 ;

  }

[nevvermind]

Your team should "look" like this:

$team1 = array("wins" => 5, "ties" => 3, "loses" => 2);

echo $team1[1]; // 3
echo $team1[0]; // 5
echo $team1["loses"]; // 2
echo $team1["wins"]; // 5

// this means "element/array with index 2 from the array index 3, from the array index 5"
$team1[5][3][2];

Google some associative and indexed arrays. With some gazillion tutorials, you can't go wrong. Play with simple PHP at first, until you get the grip.

[cneeds]

robkir;10963860 wrote:

Teams can either win, tie or lose a game. Over ten games they might have 5 wins, 3 ties and 2 loses.

Your code should look something like this:

//team1 is home team and team2 is away team
      if($score1 > $score2)
      {
      $whichTeam= $team1;  

      $teamName[$whichTeam]+=3 ;

  $team1['wins'] += 1;
  $team2['losses'] += 1;

// Tie Game      

      }
        elseif ($score1 == $score2)
      {    

        $whichTeam= $team1;  

        $teamName[$whichTeam]+=1 ;

    $whichTeam= $team2;  
    $teamName[$whichTeam]+=1 ;   
    $ties[$whichTeam]+=1;

   $team1['ties'] += 1;
   $team2['ties'] += 1;


//Who was the winner, team two        

      }
        elseif($score1 < $score2)
      {       

        $whichTeam = $team2;
        $teamName[$whichTeam]+=3 ;

   $team2['wins'] += 1;
   $team1['losses'] += 1;

  } 

You only need a one dimensional array for each team, unless you want to put the teams in as well, ie.

$teamName[$team1]['wins'] += 1;

But here I'm guessing so you better confirm that it's gonna work 😉

Chris

[robkir]

I do need to keep track of the results by team number. The final output will be sorted by the team that has the most points. the user would see:

Team #7 | Wins 4 | Ties 2 | Losses 1 | Total Points 14
Team #3 | Wins 3 | Ties 2 | Losses 2 | Total Points 11

So, using your input and experimenting, the way I should go is:

$teamName[$team1]['wins'] += 1; 
$teamName[$team1]['ties'] += 1; 
$teamName[$team1]['loss'] += 1; 

I can see, using print_r that this array has the team number and the number of wins, ties and losses.

But when I use

foreach ($teamName as $key=>$value) {
	echo "Team #$key Total wins - $value <br/>";
	}

The foreach's output is: Team #1 Total wins - Array

I've read a bunch of websites, but my brain cells can't to put it all together. After the module process all the scores, how do I extract all of the array's contents?

I'll need to sort the arrays, once they are done, in order of highest points. So I plan to add the following code to calculate the points as it gathers the number of wins and ties.

$teamName[$team1]['points'] += 3; // teams earn three points for a win. 

Does that seem reasonable?

Thanks for your input. It has been most helpful.

[robkir]

Thanks Nevermind. I'll give it a try

[cneeds]

robkir;10963903 wrote:

But when I use

foreach ($teamName as $key=>$value) {
	echo "Team #$key Total wins - $value <br/>";
	}

I suspect you'll have to do another foreach for the wins, ties, losses within the teams' foreach.

Chris

[robkir]

Hi Chris,
I ended up doing this:

 echo "<table border =1>";
   echo "<tr><td>Team Number</td><td>Points</td><td>Wins</td><td>Ties</td><td>Losses</td><td>Goals Allowed</td></tr>";  

   //array_multisort($teamName);
     foreach ($teamName as $key=>$value) {
   echo "<tr><td><font color='red'>$key</font></td>";
   foreach ($value as $iKey => $iValue) {
      echo "<td>$iValue</td>";
      }
      echo "</td></tr>";
      }  

echo "</table>";

And it outputs
Team Number Points Wins Ties Losses Goals Allowed
1 6 2 0 0 2
2 0 0 2 0 1
3 1 0 1 1 3

So...I got that part mastered--my next challenge is to figure out how to get the elements to sort by Points, since the team with the most amount of points would be in the top position. If I get stuck, I'll open another thread.

Thanks again for the advice. Multi-dimensional arrays are still a sticky point for me, but I am getting a bit better.

[cneeds]

robkir;10963967 wrote:

my next challenge is to figure out how to get the elements to sort by Points

Hi Rob

It looks good.

The simplest sorting will be to put the values into a spread sheet or database but, if you want to sort in memory, you should google "bubble sort". I haven't done that in years but the principle is very simple. Just remember to keep all the values of any "level" together! (Like columns in a spreadsheet.)

BOL.

Chris

[robkir]

Hi Chris,

I looked up 'bubble sort' -- interesting routine. As it happens I solved the problem with array_multisort. The only minor downside was that it renumbers the index and the index represents the team numbers. That was easily solved by changing it to an associative array.

In case you are curious, here's the whole sorting routine

 $i=0; 

foreach ($teamName as $key => $row) {
$thisTeam[$key]  = $row[$thisTeam];
$points[$key] = $row['points'];
}


array_multisort($points, SORT_DESC, $teamName) ;
     foreach ($teamName as $key=>$value) {
     $teamIs[$i] = $key;
   foreach ($value as $iKey => $iValue) {

  $item[$i]=$iValue; $i++;

  }

  } 

Thanks again for following up. What in the heck did we ever do before the internet? I'd probably be doing needlepoint instead.

Cheers,
Rob

[johanafm]

Just a little comment. You did the right thing using array_multisort.

Bubble sort is inefficient, especially for highly unsorted data. I.e., the more out of place each array element is, the more iterations are needed by the algorithm since it goes over every element one at the time, and for each element it swaps places with its neighbour, one place at the time until it reaches its final position.
A divide-and-conquer strategy such as merge sort would be far more efficient. At least unless you are operating on sorted data.

Bubble sorting n elements takes Θ(n) for sorted data, while average and worst case runs in O(nn) and Θ(nn) respectively. Merge sort runs in Θ(n*log n) for sorted data, but so does average and worst case.
I'm no expert on sorting algorithms, but I believe it should be possible to improve on an ordinary merge sort by using insertion sort for sub problems of size < m. Just don't ask me to prove it.

Anyway, if you have to build your own sorting algorithm in php, you are at a disadvantage vs a built-in sorting algorithm which is pre-compiled. So even if you would use a more efficient sorting algorithm, it would have to operate on very large data sets and/or be a LOT more efficient to actually perform better than a precompiled sort.
While I havn't looked at how built in array sorting is implemented in PHP, I'd assume the PHP devs responsible for it are at least as knowledgeable as I am, which means there's little chance of any time complexity gains by implementing my own sort algorithm.

Conclusion: if there is a built in function, use it. Trying to be "smart" in this regard will just result in worse performance. The only reason to write your own would be if you want to experiment with sorting algorithms.

[robkir]

Hi johanafm,

Thanks for the in depth explanation. Since I am still scratching the surface with PHP I always look for the easiest route and once I dug through the tons of alternate solutions multi-sort was the only one I could get to work properly. The hardest part for me, when faced with challenges such as this, is figuring out how to phrase the googling question to get the answer that is best.

[johanafm]

The documentation at php.net is also very helpful. The functions are grouped in "books", which means that if you search for array you get directly to the "array book", but even searching for array_multisort takes you to the "array book", albeit at a different page within it. Either way, you get a list of all existing array functions and most of them makes enough sense from the function name that you will know what it does.
So somtimes this approach is easier than coming up with a googling strategy for an unknown function.

[robkir]

I never thought of doing that. I searched php.net and found the multi-sort solution in about two clicks. Live and learn...

Rob

[cneeds]

robkir;10964231 wrote:

Live and learn...Rob

Me too. Thanks guys.

Chris