What's the most efficient way to remove items from an array in php where the value is greater than a pre-determined threshold, e.g. given an array
Array
(
[0] => 1.639
[1] => 2.168
[4] => 1.897
[6] => 4.129
)
I would like to remove all the items with a value greater than e.g. 2, preserving key associations, to give
Array
(
[0] => 1.639
[4] => 1.897
)
I know I can do this using a foreach() loop but it seems that there should be a more elegant way.
No matter what you use, the array has to be looped through but you can hide it by using array_filter:
function test($var) { return $var < 2; }
$data = array_filter($data, 'test');
Related
I searched many thread but i can't find this solution
I have this Array
Array
( [0] => [1] => Array ( [0] => 2019-01-11T23:30:00CET [1] => -12.6 ) [2] => [3] => Array ( [0] => 2019-01-11T23:20:00CET [1] => -12.5 ) [4] => [5] => Array ( [0] => 2019-01-11T23:10:00CET [1] => -12.6 ) [10] => [11] => Array ( [0] => 2019-01-11T22:40:00CET [1] => -12.4 )
I found the path to have the maximum or minimum value ( Column [1] ) from this Array but i need to find the relative Parent
(example the minimum -12.6 is in the [1][0] as 2019-01-11T22:20:00CET)
of this two values that are show in the first column ( Column[0] )
Thanks
If you use array_column() to extract the second column of your data, then you can use min() or max() with that array to pick which one you want. This code then extracts the ones that match using a foreach() and if to check if it matches (not exactly sure what you want as output, but this should help)...
$source = [["2019-01-11T23:30:00CET", -12.6],
["2019-01-11T23:20:00CET", -12.5],
["2019-01-11T23:10:00CET", -12.6]
];
$extract = min(array_column($source, 1)); // or use max()
$output = [];
foreach ($source as $key => $element) {
if ( $element[1] == $extract ) {
// Matches, so add to output
$output[$key] = $element[0];
}
}
print_r($output);
will give
Array
(
[0] => 2019-01-11T23:30:00CET
[2] => 2019-01-11T23:10:00CET
)
You could use array_filter() to extract the matching rows, but a foreach() is enough for a straightforward thing like this (IMHO).
If there is a possibility of blank values or strings in the value column, this may confuse the min() as it will consider the values and compare them as strings, to ensure they are all compared as numbers you can add...
$values = array_map("floatval", array_column($source, 1));
$extract = min($values); // or use max()
The array_map("floatval",... goes through the list and converts them all to float values.
Also, here's a generalized algorithm-sketch for "finding the max in some array", expressed as pseudo-code:
"Leave quietly" if the array is empty, or throw an exception.
Otherwise, assume that the first element in the array is the biggest one.
Now, loop through the remaining elements, testing if each one is, in fact, bigger than the "biggest one" that you have so far. If so, select it as the "biggest."
When the loop is finished, return your answer.
Now – this is what a geek would call "an O(n) algorithm," which is to say that its execution-time will be "on the order of" the number of elements in the array. Well, if this is a "one-off" requirement, that's fine. Whereas if what you actually want to do is to get "more than one" max-element, sorting the array (once, then holding on to the sorted result ...) becomes significantly better, because the sort is going to be O(log(n)) ... "on the order of some logarithm of the number of elements," ... and the subsequent cost of "popping off" elements from that sorted array becomes non-existent.
There are other ways to do it, of course – trees and such - but I've already blathered-on too long here.
(
[1] => Array
(
[rules_properties_id] => 1
[operator] => >=
[value] => 2
[function] => NumOrdersPlaced
[rules_properties_params] => Array
(
[num_days] => 30
[customer_id] => 5
)
)
[2] => Array
(
[rules_properties_id] => 1
[operator] => >=
[value] => 5
[function] => NumOrdersPlaced
[rules_properties_params] => Array
(
[num_days] => 90
[customer_id] => 5
)
)
[3] => Array
(
[rules_properties_id] => 2
[operator] => >
[value] => 365
[function] => CustAcctAge
[rules_properties_params] => Array
(
[customer_id] => 5
)
)
)
That's the print_r of an array that I'm getting back from my database. I need to find the index number of the sub-array that contains the function called NumOrdersPlaced (the expected result would be 2.) Is the only way to do this by looping through the array and subarrays and comparing (as in this answer)? Or is there a more efficient, elegant (i.e. one-liner) function available that I don't know about?
No, there is no one liner for searching multidimensional arrays in PHP, expect you'll write a function for it yourself and use it as one liner :)
Approaches would be:
Change the data structure to somewhat that is good for search operations. eg xml with xpath
When creating the array from your question, create another array which indexes are the function names, and which values are pointers to the sub arrays of the original array
Use the database for that operations. It's optimized for it
...
When searching for the 'right' way you'll have to find a compromise between performance of search, insert, update, remove operations, memory consumption and ease of usage.
As you asked for a PHP solution, here comes an example how I would do it in PHP using and additional index array: (approach 2. from the list above)
// we need two arrays now:
$data = array();
$index = array();
// imagine you loop through database query results
foreach($db_result as $record) {
// create a copy of $record as the address
// of record will contain the last(!) element agter foreach
$item = $record;
// store pointers to that array in data and index
$data []= &$item;
$index[$item->function] = &$item;
}
// here is your one liner
$found = isset($index['NumOrdersPlaced']) ? $index['NumOrdersPlaced'] : NULL;
// another index seach:
$found = isset($index['CustAcctAge']) ? $index['CustAcctAge'] : NULL;
// note there is no additonal loop. The cost is the
// additional memory for $index
Given
[0] => Array
(
[0] => ask.com
[1] => 2320476
)
[1] => Array
(
[0] => amazon.com
[1] => 1834593
)
[2] => Array
(
[0] => ask.com
[1] => 1127456
)
I need to remove duplicate values solely based on first value, regardless of what any other subsequent values may be. Notice [0][1] differs from [2][1] yet I consider this as a duplicate because there are two matching first values. The other data is irrelevant and shouldn't be considered in comparison.
Try this, assuming that $mainArray is the array you have.
$outputArray = array(); // The results will be loaded into this array.
$keysArray = array(); // The list of keys will be added here.
foreach ($mainArray as $innerArray) { // Iterate through your array.
if (!in_array($innerArray[0], $keysArray)) { // Check to see if this is a key that's already been used before.
$keysArray[] = $innerArray[0]; // If the key hasn't been used before, add it into the list of keys.
$outputArray[] = $innerArray; // Add the inner array into the output.
}
}
print_r($outputArray);
So here's what I see this code doing:
An array is made
A loop iterates 10 times
A new array is created
A reference to this new array is saved in the first array
10 arrays now reside in the original array with values 0, 1, 2, 3...
What really happens:
WTF?
Code:
<?php
header('Content-type: text/plain');
$arrays = array();
foreach(range(0, 10) as $i)
{
$arr = array();
$arr[0] = $i;
$arrays[] = &$arr;
}
print_r($arrays);
Output:
Array
(
[0] => Array
(
[0] => 10
)
[1] => Array
(
[0] => 10
)
[2] => Array
(
[0] => 10
)
[3] => Array
(
[0] => 10
)
[4] => Array
(
[0] => 10
)
[5] => Array
(
[0] => 10
)
[6] => Array
(
[0] => 10
)
[7] => Array
(
[0] => 10
)
[8] => Array
(
[0] => 10
)
[9] => Array
(
[0] => 10
)
[10] => Array
(
[0] => 10
)
)
I would like to know exactly why apparently only the 10th array is referred to ten times, instead of every instance of the arrays being referred to one each.
Also if somebody who isn't just thinking WTF (like me) would like to edit the title, feel free to do so.
The line
$arr = array();
does not create a new array but rather assigns an empty array to the already existing reference.
If you want the variable name to "point" to a different array in memory, you have to unset() (or "disconnect") it first before assigning an empty array to it:
foreach(range(0, 10) as $i)
{
unset($arr);
$arr = array();
$arr[0] = $i;
$arrays[] = &$arr;
}
This is because the only operations that can make a variable point to something else is the reference assignment (=&) and the unset().
What happens here is that by inserting a reference to $arr inside $arrays, you are effectively adding the exact same array 10 times -- and each reference to the array has the value last assigned to it (i.e. the one produced when $i is 10).
It's not clear what you intend to achieve by inserting a reference in each iteration -- either removing the & or putting unset($arr) at the beginning of the loop would give you the expected behavior. What are you trying to accomplish?
Think about it this way. You do $arrays[] = &$arr; 10 times. This stores a reference to the local variable $arr 10 times. Since it's the same variable (the variable's scope is the entire function), it stores the same reference all 10 times. Thus, why should you expect the 10 elements to be different?
The reference you are storing has nothing to do with the value of $arr; it just has to do with the variable $arr. When you print the reference it prints the value of $arr at that time.
It's because you're storing a reference to the array that $arr points to in the array. And you keep overwriting that array with the latest number. All references in $arr will point to the same array in the end.
I don't know what you expect to get out of this in the end, but getting rid of & should fix this behavior.
I'm a bit struggling with the associative arrays in associative arrays. Point is that I always have to drill deeper in an array and I just don't get this right.
$array['sections']['items'][] = array (
'ident' => $item->attributes()->ident,
'type' => $questionType,
'title' => $item->attributes()->title,
'objective' => (string) $item->objectives->material->mattext,
'question' => (string) $item->presentation->material->mattext,
'possibilities' => array (
// is this even neccesary to tell an empty array will come here??
//(string) $item->presentation->response_lid->render_choice->flow_label->response_label->attributes()->ident => (string) $item->presentation->response_lid->render_choice->flow_label->response_label->material->mattext
)
);
foreach ($item->presentation->response_lid->render_choice->children() as $flow_label) {
$array['sections']['items']['possibilities'][] = array (
(string) $flow_label->response_label->attributes()->ident => (string) $flow_label->response_label->material->mattext
);
}
So 'possibilities' => array() contains an array and if I put a value in it like the comment illustrates I get what I need. But an array contains multiple values so I am trying to put multiple values on the position $array['sections']['items']['possibilities'][]
But this outputs that the values are stores on a different level.
...
[items] => Array
(
[0] => Array
(
[ident] => SimpleXMLElement Object
(
[0] => QTIEDIT:SCQ:1000015312
)
[type] => SCQ
...
[possibilities] => Array
(
)
)
[possibilities] => Array
(
[0] => Array
(
[1000015317] => 500 bytes
)
[1] => Array
...
What am trying to accomplish is with my foreach code above is the first [possibilities] => Array is containing the information of the second. And of course that the second will disappear.
Your $array['sections']['items'] is an array of items, so you need to specify which item to add the possibilities to:
$array['sections']['items'][$i]['possibilities'][]
Where $i is a counter in your loop.
Right now you are appending the Arrays to [items]. But you want to append them to a child element of [items]:
You do:
$array['sections']['items']['possibilities'][] = ...
But it should be something like:
$array['sections']['items'][0]['possibilities'][] = ...
$array['sections']['items'] is an array of items, and as per the way you populate the possibilities key, each item will have it's own possibilities. So, to access the possibilities of the item that is being looped over, you need to specify which one from $array['sections']['items'] by passing the index as explained in the first answer.
OR
To make things simpler, you can try
Save the item array (RHS of the first =) to a separate variable instead of defining and appending to the main array at the same time.
Set the possibilities of that variable.
Append that variable to the main $array['sections']['items']
I have:
array[{IsChecked: true, SEC: 0, STP: 0},
{IsChecked: ture ,SEC: 0, STP: 1},
{IsChecked: false, SEC: 1 ,STP: 0}]
How to get each SEC where IsCheked value is true?