Assign maximum temperature to a specific day in multidimensional array - php

Question

I'm sure that the title is a bit of vague, but i hope that the example will explain the issue better.
So, I have an array that contains a list of 40 results. In each of the results, there is a timestamp, which i translate to a specific day, like "monday" and a temperature. The thing is that, there can be up to 8 time periods in one day. And a temperature for each period. I somehow have to determine how to asign a maximum temperature for a specific day based on all of the temperatures related to that day.
So, the array looks something like this:
array (size=40)
0 =>
'dt' => int 1530802800
'main' =>
'temp' => float 29.14
1 =>
'dt' => int 1530813600
'main' =>
'temp' => float 25.63
...
And what i would like to achieve something like this:
array
monday => 27.65
tuesday => 24.65
...
I'm able to create two separate arrays that hold all the days and all of the temperatures, but i'm not sure how to bind all of the temperatures related to a specific day, since i can have the same day appear in that array up to 8 times, and then calculate the highest temperature for that day.
I have something like:
0 => monday
1 => monday
2 => monday
3 => tuesday
and another array is:
0 => 23.56
1 => 34.66
2 => 12.44
3 => 34.44
What i would like is to at least have something like this
monday => array(
0 => 23.56
1 => 34.66
2 => 12.44
),
tueasday => array(
0 => 34.56
1 => 34.66
2 => 13.44
)
...
Hope that was clear enough.
Any help is appreciated.
Thanks.

Answer 1

Starting from your original array (not the two separate ones). Get the day from the timestamp and assign that as the key of the result. Check if the current value is less and if so replace with the new one:
foreach($array as $values) {
$day = strtolower(date('l', $values['dt']));
if(!isset($result[$day]) || $result[$day] < $values['main']['temp']) {
$result[$day] = $values['main']['temp'];
}
}
You could also create an array keyed by the day with all temperatures:
foreach($array as $values) {
$day = strtolower(date('l', $values['dt']));
$result[$day][] = $values['main']['temp'];
}
Then compute the maximums for each day:
$max = array_map('max', $result);

Answer 2

It looks like the concept you're missing to accomplish this is dynamically constructing an array from keys.
If you iterate your original array, convert the timestamp to a day. You've said you already know how to do that. Then use that day as the key to construct your result array.
foreach ($data as $measurement) {
$day = however_you_convert($measurement['dt']);
// ↓ defines the group
$result[$day][] = $measurement['main']['temp'];
// ↑ adds the value to an array under that group
}
That will convert your data to the grouped structure shown in the last code block in your question. From there, you can use sort or max to get the highest value.
If you don't need the sets of values, you can just keep track of the max value as you go, like this other answer shows.

Answer 3

now that you have this:
$days = ["0" => "monday",
"1" => "monday",
"2" => "monday",
"3" => "tuesday"];
$temps = [
0 => 23.56,
1 => 34.66,
2 => 12.44,
3 => 34.44
];
you can do this:
$result = [];
foreach($days as $key => $day){
if(!isset($result[$day]))
$result[$day] = $temps[$key];
if($temps[$key] > $result[$day])
$result[$day] = $temps[$key];
}
var_dump($result);
output:
array(2) {
["monday"]=>
float(34.66)
["tuesday"]=>
float(34.44)
}
Hope it helps you arrive at a optimal solution.

Answer 4

Based of what you show us :
$days = array(
0 => 'monday',
1 => 'monday',
2 => 'monday',
3 => 'tuesday'
);
$temp = array(
0 => 23.56,
1 => 34.66,
2 => 12.44,
3 => 34.44
);
If you are sure that you have 2 array with the same size :
$new_array = array();
foreach ($days as $key=> $day) {
$new_array[$day][] = $temp[$key];
}
var_dump($new_array);
The output is :
array (size=2)
'monday' => array (size=3)
0 => float 23.56
1 => float 34.66
2 => float 12.44
'tuesday' => array (size=1)
0 => float 34.44
Now if you want an array with the day and the max temp of each day :
$result = array();
foreach($new_array as $day => $temp_array) {
$result[$day] = max($new_array[$day]);
}
var_dump($result);
The output is :
array (size=2)
'monday' => float 34.66
'tuesday' => float 34.44
There is maybe a better way to achieve it but according to your question and what you ask for it should do the job, I hope it helps !