current community

your communities

more stack exchange communities

Stack Exchange
tour help
careers 2.0
Take the 2-minute tour ×
Stack Overflow is a question and answer site for professional and enthusiast programmers. It's 100% free, no registration required.
up vote 1 down vote favorite
1

I need help once again. I have an array and I need to extract earliest day weight value.

EDIT - EDIT - EDIT


array (
  3 => 
  array (
    'id' => '20110211',
    'Date' => '2011-02-11',
    'Weight' => '195',
  ),
  4 => 
  array (
    'id' => '20110213',
    'Date' => '2011-02-13',
    'Weight' => '160',
  ),
  6 => 
  array (
    'id' => '20110310',
    'Date' => '2011-03-10',
    'Weight' => '200',
  ),
  12 => 
  array (
    'id' => '20110301',
    'Date' => '2011-03-01',
    'Weight' => '55',
  ),
  21 => 
  array (
    'id' => '20110215',
    'Date' => '2011-02-15',
    'Weight' => '120',
  ),
  25 => 
  array (
    'id' => '20110322',
    'Date' => '2011-03-22',
    'Weight' => '250',
  ),
)

I've edited this and this code works:


function sortByDate ($arr1, $arr2)
{
   return strcmp($arr1['Date'], $arr2['Date']);
}
// $arr is your array
usort($weight_tracker, 'sortByDate');
$earliest = $weight_tracker[0]['Weight'];
echo $earliest;

But since I have a form on this page which updates the array when array is updated - I got message Fatal error: Cannot use string offset as an array in

EDIT -> I've re-declared this as string, hence the ERROR ! be careful when using global and includes as everything can become a mess ! PHP is forgiving, but that "forgiveness" can cost a lot of time later on... :)

Thanks,
Peter

share|improve this question
    
It would be easier for others to copy your code and work out a solution if you pasted properly formed arrays in PHP rather than the result of var_dump(), it means we have to type them out ourselves, just saying... –  Cups May 3 '11 at 15:25
    
This may be a dumb question, but is $weight_tracker being accidentally reassigned to a string instead of array at some point? If this code is where the error occurs, it sounds like it's because $weight_tracker is a string when it should be an array. –  Wiseguy May 3 '11 at 16:54
    
On an unrelated note, it looks like the numeric keys in the big array are record IDs from a DB or something. Do those need to be preserved? Currently usort() renumbers them 0,1,2,etc. If you need to keep the original ID numbers, I'll update my answer for that. –  Wiseguy May 3 '11 at 16:56
    
@Cups - I know, but I'm not sure if I can paste 600 lines of code... @Wiseguy - I'm looking at the code to see, but I think it's not reassigned to a string.... For this stuff I just need an Weight value recorded on earliest date (order and ID's are not important as the ID is actually a time-stamp for now but later on will be used for something different) –  Peter May 3 '11 at 17:01
    
ABSOLUTELY CORRECT - I had an include where I re-declared it as a STRING :( MY BAD !!! THIS IS 100% WORKING SOLUTION ! –  Peter May 3 '11 at 17:32
add comment

4 Answers

up vote 2 down vote accepted

You could sort the array with a custom callback using usort() and then take the first element.

// $arr is your array
usort($arr, 'sortByDate');
$earliest = $arr[0];

function sortByDate ($arr1, $arr2)
{
   return strcmp($arr1['Date'], $arr2['Date']);
}
share|improve this answer
    
This works, but when page is updated I get Fatal error: Cannot use string offset as an array in... I've updated it in question –  Peter May 3 '11 at 16:38
    
@Peter I don't see how this code would cause that error. Is it from something you added right after it? Maybe this will help. –  Wiseguy May 3 '11 at 16:43
    
Great... my bad - in one included file I've re-declared it as string - THANKS FOR HELP ! –  Peter May 3 '11 at 17:33
add comment
up vote 1 down vote

This is one way of doing it:

function filter_min($a, $b) {
  return ($a['Date'] < $b['date']) ? $a : $b;
}

$result = array_reduce($array, 'filter_min');
echo $result['Weight'];

Another way is to simply iterate over the array and find the smallest date.

share|improve this answer
add comment
up vote 0 down vote 
$smallest = null; // array index of entry with smallest weight.
foreach ($array as $idx => $data) {
    if (($data['Weight'] < $array[$smallest]['Weight']) || (is_null($smallest))) {
      $smallest = $idx; // found a small weight, so save the index
    }
}

echo $array[$smallest]['Date'];
share|improve this answer
add comment
up vote 0 down vote

I noticed that the dates are in reverse order with the latest date being pulled in first, and the earliest date last. Will it always be like that? If so, you can do this:

$index = count($array) - 1;
$earliestdate = $array[$index]['Date'];

You could also use array_reverse() to invert the array and make the first element the formerly last element.

If this is being pulled in from MySQL you could also alter the query to ORDER BY 'Date' DESC (or is it ASC that would get you what you want, can't remember)

share|improve this answer
    
Actually, they're not in order, but I agree with ordering in the DB query if possible/applicable. –  Wiseguy May 3 '11 at 15:43
    
Ah, you're right, didn't notice that 02-05-2011 was before 02-10-2011 –  Phoenix May 3 '11 at 15:46
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.