how to find the number of repeating strings and their array index in a string array in matlab

Question

I have a long array (1x75000 !) of string data. In this array, there are repeated strings. i want to find the array indices and the number of each repeating string. E.g.

A=['abc' 'efg' 'hij' 'abc' 'hij' 'efg' 'klm']; the answer should be: 2 times 'abc' at array indices 1, 4 2 times 'efg' at array indices 2, 6 2 times 'hij' at array indices 3, 5 1 time 'klm' at array indices 7

notice the large size of the array (1x75000)

Answer 1

This code should work:

<?php

$array = array('abc','wrerwe','wrewer','abc');
$out = array();

foreach ($array as $key => $value) {
    if (!isset($out[$value]))  {
        $out[$value]['nr'] = 0;
        $out[$value]['index'] = array();        
    }
    ++$out[$value]['nr'] ;
    $out[$value]['index'][] = $key;
}


foreach ($out as $k => $v) {
    echo "item ".$k." repeats ".$v['nr'].' times at positions: ';
    echo implode(', ', $v['index']);
    echo "<br />";
}

But so far I haven't tested in on such big array. In fact I don't think you should operate on such big arrays. You should rather divide it on smaller arrays.

I've tested it on 75000 array using code ( source for generating random string from How to create a random string using PHP? ) :

<?php

$array = randomTexts(75000);
$out =  array();

foreach ($array as $key => $value) {
    if (!isset($out[$value]))  {
        $out[$value]['nr'] = 0;
        $out[$value]['index'] = array();        
    }
    ++$out[$value]['nr'] ;
    $out[$value]['index'][] = $key;
}


foreach ($out as $k => $v) {
    echo "item ".$k." repeats ".$v['nr'].' times at positions: ';
    echo implode(', ', $v['index']);
    echo "<br />";
}


function randomTexts($nr) {
    $out = array();
    $validString = 'abddefghihklmnopqrstuvwzyx';
    for ($i=0; $i< $nr; ++$i) {
        $len = mt_rand(5,10);        
           $out[] = get_random_string($validString, $len);
    }
    return $out;
}


function get_random_string($valid_chars, $length)
{
    // start with an empty random string
    $random_string = "";

    // count the number of chars in the valid chars string so we know how many choices we have
    $num_valid_chars = strlen($valid_chars);

    // repeat the steps until we've created a string of the right length
    for ($i = 0; $i < $length; $i++)
    {
        // pick a random number from 1 up to the number of valid chars
        $random_pick = mt_rand(1, $num_valid_chars);

        // take the random character out of the string of valid chars
        // subtract 1 from $random_pick because strings are indexed starting at 0, and we started picking at 1
        $random_char = $valid_chars[$random_pick-1];

        // add the randomly-chosen char onto the end of our string so far
        $random_string .= $random_char;
    }

    // return our finished random string
    return $random_string;
}

It also seems to work but it takes a few seconds