algorithm implementation problem

morgn

hi,
basically i need an algorithm that will count the frequency of each date stored in a database. The database is storing votes and they want to see number of votes per day.
i come from a java background and havent touched that in a year and i think im getting confused..

the pseudo code:
1. get all dates from db,
2. put into array
3. get first date
4. while there are more of that date in array, counter ++
5. print date and counter
6. remove that date from array
7. go to part 3

i think this will work, but im stuck on the implementation. can anyone point me to any tutorials or code that will help?

cheers,
morgn.

LordShryku

That seems overly complicated. You could just group it in the SQL.

  SELECT date_field, count(*)
    FROM table
GROUP BY date_field

drew010

you could do something like this:

$q = "SELECT datefield FROM table";
$r = mysql_query($q);

$counts = array();

while($data = mysql_fetch_row($r)) {
    if(array_key_exists($data[0], $counts)) {
        //date is in the array already
        $counts[$data[0]]++;
    } else {
        //no count for this date yet
        $counts[$data[0]] = 1;
    }
}

arsort($counts, SORT_NUMERIC);
//sort descending

foreach($counts as $date => $count) {
    echo "$count votes on $date<br />\n";
}

morgn

wow.

LordShryku - i cant believe how simple that is. it seems to work. im not sure how it will display because there is only one date in the database at the moment.

i have got it printing that one out to the web page, but im not sure how i break the count from the group of dates so that i can format the page correctly. is that to do with list (var, val)?

drew010 - although i dont fully understand what is going on i assume that the script is doing eaxcly what my pseudo code says. im working though it. i have more control over the output too.

thankyou both for replying, its opened a can of worms, but thats a good thing!

cheers,
Morgn.

drew010

hi. i can document my code better in case you decide to use it in the production.

basically all it does is query the database for the date.
then while data is coming from sql it looks at the date (maybe in the form of mm-dd-yyyy) and checks our array $counts, for an index with that date. i.e. $array["04-22-2004"] = 5
if array_key_exists, it means that we already have counted one for that date so it should be incremented, otherwise it creates a new array element with that date as the key and then assigns 1 to it.
it continues this until no more data is coming from mysql.
then it sorts the array in reverse order (desc) preserving the keys with their counts.
then the foreach just goes thru all the values and assigns the key (the date) to $date and the value (the count) to $votes and prints out x votes on date.

simple as that 🙂
good luck

morgn

aha! so the array acts in reverse of what i had imagined. and more logical too.
nice one.
thanks very much.