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Thread: Sorting arrays

Jan 21, 2005, 14:25 #1
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Sorting arrays
Hi Guys,
I have a little trouble and i'm in need of some help.
I have an array that i have created and is layed out below. I think they call this multi dimensional.
$entries[customerid][x_cord]
$entries[customerid][y_cord]
$entries[customerid][dist]
The sample values are as follows:
$entries[1][x] = 10
$entries[1][y] = 50
$entries[1][dist] = 60
$entries[2][x] = 20
$entries[2][y] = 20
$entries[2][dist] = 40
$entries[3][x] = 40
$entries[3][y] = 10
$entries[3][dist] = 50
The out come i'm after is to sort this array on the [dist] part of the array so the lowset value is at the top of the array ie. the first row but i'm not sure how to achieve this.
If you can help i'd be very greatful
Thank in advance
Matt

Jan 21, 2005, 14:43 #2

Jan 21, 2005, 16:41 #3
Not sure if array_multisort will work  haven't tested it, but if it doesn't, try this code
PHP Code:$entries[1]['x'] = 10;
$entries[1]['y'] = 50;
$entries[1]['dist'] = 60;
$entries[2]['x'] = 20;
$entries[2]['y'] = 20;
$entries[2]['dist'] = 40;
$entries[3]['x'] = 40;
$entries[3]['y'] = 10;
$entries[3]['dist'] = 50;
function cmp ($Array1, $Array2)
{
return ($Array1['dist']  $Array2['dist']);
}
usort($entries, 'cmp');
print_r($entries);

Jan 21, 2005, 17:07 #4
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or, to refine swdev's idea
PHP Code:usort($entries, create_function('$a,$b','return ($a["dist"]$b["dist"]);'));
Jason Sweat ZCE  jsweat_php@yahoo.com
Book: PHP Patterns
Good Stuff: SimpleTest PHPUnit FireFox ADOdb YUI
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Jan 22, 2005, 11:37 #5
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I'm really sorry guys but i'm not getting this. I've had a little rethink though.
This is what i've got. I have a table of tickets sold and they include the customerid and some x and y values. What i want to do is query the table and build an array where i get a key = to customerid and a value of the below calculation.
$sum = sqrt(pow($xvalue) + pow($yvalue));
so it should resemble something like this.
Key Value
$array[0001] = 12
$array[0002] = 15
$array[0003] = 20
Then i just want to evaluate which one of these is closest to my winning value.
$winner = 16
I know how to do closest using a subtraction and it using abs() so they are all positive. Then i can work out the smallest difference.
So the end result should be a result of customer id 0002 being the winner.
If you can help i would be so greatful.
Thanks guys, your comments have been great i'm just sorry i don't understand.

Jan 22, 2005, 16:58 #6
The pow function takes 2 parameters.
I'm not sure if this is what you want but try this code
PHP Code:// Required winning value  change as required
$winning_value = 16;
// Actual winning value  do not change
$actual_winning_value = 1;
// winning customer id  do not change
$winning_id = 1
// current difference between this guess and current winning guess  do not change
$curr_diff = 999999;
$sql = 'SELECT '
. ' customer_id, xvalue, yvalue'
. ' FROM'
. ' ticket_table'
;
/* ***** START DIAGNOSTIC ***** */
echo 'Executing ' . $sql . '<br />';
/* ***** END DIAGNOSTIC ***** */
$result = mysql_query($sql) or die ('Failed to execute ' . $sql . ' due to ' . mysql_error());
while ($row = mysql_fetch_assoc($result))
{
// calculate value
$v = sqrt ( pow(intval($row['xvalue']), 2) + pow(intval($row['yvalue']), 2) );
// work out difference from real winning value
$diff = abs($v  $winning_value);
// if this is a closer guess
if ($diff < $curr_diff)
{
// save this data
$curr_diff = $diff;
$winning_id = $row['dustomer_id'];
$actual_winning_value = $v;
}
}
// display winning information
if (1 == $winning_id)
{
echo ' There were no winners<br />';
}
else
{
if ($actual_winning_value == $winning_value)
{
echo 'Winner is customer id ' . $winning_id . '<br />';
}
else
{
echo ' Nearest winner is customer id ' . $winning_id . ' with a value of ' . $actual_winning_value . '<br />';
}
}
Hope this helps

Jan 23, 2005, 05:22 #7
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Thanks swdev,
That code looks great. Also, thank you for the comments too.
I'll give this a go and let you know how i get on.

Jan 23, 2005, 10:31 #8
Thanks for the kind words. I hope it does the job

Jan 28, 2005, 14:18 #9
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Another problem
This code works great, it works out exactly as i want but i still have a problem.
I used the <input type=image> html to pass through two coordinates but it looks like this might be wrong.
This is the layout i have i think
0 






100_________________
0 100
I think this is the diagram i need.
100





________________
0 100
My question is how do i get a image map using this axis instead of the top one. The top one screws my calculation that i use (As shown by swdev).

Jan 28, 2005, 16:40 #10
Not sure i fully understand what you are asking, but trying to remember my maths from way too many years ago ) ) you could replace the yvalue with 1 * the current yvalue
e.g current_yvalue = 80, multiply it by 1 to get 80. The pow function will still give the same result.
Try it and let us know if it works.

Jan 28, 2005, 17:23 #11
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I'll try and explain a bit better.
I'm not sure if this is the right way round or not but i'll use x as horizontal and y as vertical.
What i want is the bottom left corner to be value 0 for both axis and the top of Y = to be the height in pixels of the image and the far right or X to be what ever the image pixel is. It should look like this. I'll use the value of 250 for each in this example.
Graph 1
250






0250
instead using the <input> tag uses this layout.
Graph 2
0






250
0250
This means that if i use your code from above and you have the following positions using the second graph i get the wrong winner.
Winner = 200 x 50
User1 = 20 x 230
User2 = 230 x 20
The final value using the pow() and sqrt() calculation you get
Winner = 206.15528128088
User1 = 230.8679276123
User2 = 230.8679276123
As you can see User1 and User2 have the same values. This is right using graph 2 but if you've drawn this you'll see that user 2 is the actual winner. This leads me to the conclusion i need graph 1 to make this work but there must be a sum i can do to make graph 2 work as i can't change how the X and Y's are setup.
Sorry for this being so long but just trying to make this clear, i hope this has helped.

Jan 28, 2005, 17:48 #12
Ok  I think I follow what you want.
You need to replace the yvalue with yvalue  maxyvalue
In your example, max_yvalue = 250
So
Original Data
Winner = 200 x 50
User1 = 20 x 230
User2 = 230 x 20
becomes
Winner = 200 x (50  250) = 200 x 200 = 282.84271247
User1 = 20 x (230  250) = 20 x 20 = 28.284271247
User2 = 230 x (20  250) = 20 x 230 = 230.86792761
hence User2 is the winner!
Essentially, from a graphical point of view, you are moving the displacing the y axis.
hope this helps
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