CODEWITHSUNDEEP
phparraysfilteringnegative-numberarray-filter
Ripa Saha
Ripa Saha

Reputation: 2540

Extract negative and non-negative values from an array

I need to divide an array into two arrays.

One array will contain all positive values (and zeros), the other all negative values.

Example array:

$ts = [7,-10,13,8,0,4,-7.2,-12,-3.7,3.5,-9.6,6.5,-1.7,-6.2,7];

Negatives result array:

[-10,-7.2,-12,-3.7,-9.6,-1.7,-6.2];

Non-negatives result array:

[7,13,8,0,4,3.5,6.5,7];

Upvotes: 8

Views: 5536

Answers (5)

mickmackusa
mickmackusa

Reputation: 47902

Rather than declaring two arrays, I recommend declaring one array with two subarrays. You can either give the subarrays an index of 0 or 1 depending on the conditional evaluation with zero, or you can go a little farther by declaring a lookup array to replace the integer key with an expressive word.

Regardless of if you choose to create one array or two arrays, you should only make one loop over the input array. Making two loops or by calling array_filter() twice is needlessly inefficient.

Code: (Demo)

$ts = [7,-10,13,8,4,-7.2,-12,-3.7,3.5,-9.6,6.5,-1.7,-6.2,7];
const KEY_NAMES = [0 => 'negative', 1 => 'non-negatuve'];

$result = [];
foreach ($ts as $v) {
    $result[KEY_NAMES[$v >= 0]][] = $v;
}

var_export($result);

Output:

array (
  'non-negatuve' => 
  array (
    0 => 7,
    1 => 13,
    2 => 8,
    3 => 4,
    4 => 3.5,
    5 => 6.5,
    6 => 7,
  ),
  'negative' => 
  array (
    0 => -10,
    1 => -7.2,
    2 => -12,
    3 => -3.7,
    4 => -9.6,
    5 => -1.7,
    6 => -6.2,
  ),
)

Upvotes: 0

Shankar Narayana Damodaran
Shankar Narayana Damodaran

Reputation: 68486

Without using any array functions..

Pretty straightforward. Just loop through the array and check if the number is less than 0, if so , push it in the negative array else push it in the positive array.

<?php
$ts=array(7,-10,13,8,4,-7.2,-12,-3.7,3.5,-9.6,6.5,-1.7,-6.2,7);
$pos_arr=array(); $neg_arr=array();
foreach($ts as $val)
{
    ($val<0) ?  $neg_arr[]=$val : $pos_arr[]=$val;
}
print_r($pos_arr);
print_r($neg_arr);

OUTPUT :

Array
(
    [0] => 7
    [1] => 13
    [2] => 8
    [3] => 4
    [4] => 3.5
    [5] => 6.5
    [6] => 7
)
Array
(
    [0] => -10
    [1] => -7.2
    [2] => -12
    [3] => -3.7
    [4] => -9.6
    [5] => -1.7
    [6] => -6.2
)

Upvotes: 13

Ja͢ck
Ja͢ck

Reputation: 173572

Food for thought, you could write a generic function that splits an array based on a boolean result:

// splits an array based on the return value of the given function
// - add to the first array if the result was 'true'
// - add to the second array if the result was 'false'
function array_split(array $arr, callable $fn)
{
    $a = $b = [];
    foreach ($arr as $key => $value) {
        if ($fn($value, $key)) {
           $a[$key] = $value;
        } else {
           $b[$key] = $value;
        }
    }
    return [$a, $b];
}

list($positive, $negative) = array_split($ts, function($item) {
    return $item >= 0;
});
print_r($positive);
print_r($negative);

Demo

Upvotes: 4

arkascha
arkascha

Reputation: 42925

The most elegant is to use phps array_filter() function: 

<?php

$ts = [ 7,-10,13,8,4,-7.2,-12,-3.7,3.5,-9.6,6.5,-1.7,-6.2,7 ];  

print_r( array_filter( $ts, function( $val ) { return   (0>$val); } ) );
print_r( array_filter( $ts, function( $val ) { return ! (0>$val); } ) );

?>

If you are still using an older php version you need some longer implementation: 

<?php

$ts = array( 7,-10,13,8,4,-7.2,-12,-3.7,3.5,-9.6,6.5,-1.7,-6.2,7 );  

print_r( array_filter( $ts, create_function( '$val', 'return   (0>$val);' ) ) );
print_r( array_filter( $ts, create_function( '$val', 'return ! (0>$val);' ) ) );

?>

Upvotes: 4

Rikesh
Rikesh

Reputation: 26431

You can use array_filter function,

$positive = array_filter($ts, function ($v) {
  return $v > 0;
});

$negative = array_filter($ts, function ($v) {
  return $v < 0;
});

Note: This will skip values with 0, or you can just change condition to >=0 in positive numbers filter to considered in positive group.

DEMO.

Upvotes: 8

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