I've currently got 2 dates in PHP - a 'start' date and an 'end' date. I have then created an array of dates, using a function I found called createDateRangeArray ($date_range). For simplicity, the end date will always be today's date.
I've also got a separate array that contains a bunch of dates ($valid_dates) that will always fall between the start and end dates mentioned above. On those dates, 'something' happened - in this case, a training session.
I'm trying to get my head around getting the following:
A range of dates similar to the $date_range array, populated with TRUE or FALSE based on whether or not a training session happened on that date. I'm happy for this to be an assoc array with keys named date and, say, session_found (bool).
The longest 'streak' i.e. the longest consecutive number of days that training sessions occurred.
The longest 'slump' i.e. the longest consecutive number of days that training sessions did NOT occur.
Can someone point me in the right direction for getting the above info without using a foreach on the contents of the $date_range array and then having to use another foreach for the $valid_dates array on each item in the $date_range array? That is horribly inefficient ...
Sorry if I've over-complicated things with all that info but any help would be much appreciated.
I'm currently using PHP 5.4 on Debian Wheezy, if that helps (typical LAMP stack).
Thanks
This is completely untested, but how about something like the following:
You should get the end date of the longest streak and slump, as well as how many days it took. $sessions will contain an array with the dates as the keys, and true for days with sessions, and false for days without.
Still a foreach, but I dont think you can avoid using one. Let me know if it works, I really dont have any idea how well this code will behave, but hopefully will give you a starting point?
$streak = 0;
$slump = 0;
$longeststreak = 0;
$longestslump = 0;
$longeststreakend = 0;
$longestslumpend = 0;
foreach ($date_range as $date) {
if (in_array($date, $valid_date)) {
$sessions[$date] = true;
$streak++;
// Slump broken, record the length if it beat the previous record
if ($longestslump < $slump) {
$longestslump = $slump;
$longestslumpend = $date;
}
$slump=0;
}
else {
$sessions[$date] = false;
$slump++;
// Streak broken, record the length if it beat the previous record
if ($longeststreak < $streak) {
$longeststreak = $streak;
$longeststreakend = $date;
}
$streak=0;
}
}
Related
I have PHP array which I use to draw a graph
Json format:
{"y":24.1,"x":"2017-12-04 11:21:25"},
{"y":24.1,"x":"2017-12-04 11:32:25"},
{"y":24.3,"x":"2017-12-04 11:33:30"},
{"y":24.1,"x":"2017-12-04 11:34:25"},
{"y":24.2,"x":"2017-12-04 11:35:35"},.........
{"y":26.2,"x":"2017-12-04 11:36:35"}, ->goes up for about a minute
{"y":26.3,"x":"2017-12-04 11:37:35"},.........
{"y":24.1,"x":"2017-12-04 11:38:25"},
{"y":24.3,"x":"2017-12-04 11:39:30"}
y=is temperature and x value is date time,
as you can see temperature doesn't change so often even if, it change only for max 0.4. But sometimes after a long period of similar values it change for more than 0.4.
I would like to join those similar values, so graph would not have 200k of similar values but only those that are "important".
I would need an advice, how to make or which algorithm would be perfect to create optimized array like i would like.
perfect output:
{"y":24.1,"x":"2017-12-04 11:21:25"},.........
{"y":24.1,"x":"2017-12-04 11:34:25"},
{"y":24.2,"x":"2017-12-04 11:35:35"},.........
{"y":26.2,"x":"2017-12-04 11:36:35"}, ->goes up for about a minute
{"y":26.3,"x":"2017-12-04 11:37:35"},.........
{"y":24.1,"x":"2017-12-04 11:38:25"}
Any help?
As you specified php I'm going to assume you can handle this on the output side.
Basically, you want logic like "if the absolute value of the temperature exceeds the last temperature by so much, or the time is greater than the last time by x minutes, then let's output a point on the graph". If that's the case you can get the result by the following:
$temps = array(); //your data in the question
$temp = 0;
$time = 0;
$time_max = 120; //two minutes
$temp_important = .4; //max you'll tolerate
$output = [];
foreach($temps as $point){
if(strtotime($point['x']) - $time > $time_max || abs($point['y'] - $temp) >= $temp_important){
// add it to output
$output[] = $point;
}
//update our data points
if(strtotime($point['x']) - $time > $time_max){
$time = strtotime($point['x']);
}
if(abs($point['y'] - $temp) >= $temp_important){
$temp = $point['y'];
}
}
// and out we go..
echo json_encode($output);
Hmm, that's not exactly what you're asking for, as if the temp spiked in a short time and then went down immediately, you'd need to change your logic - but think of it in terms of requirements.
If you're RECEIVING data on the output side I'd write something in javascript to store these points in/out and use the same logic. You might need to buffer 2-3 points to make your decision. Your logic here is performing an important task so you'd want to encapsulate it and make sure you could specify the parameters easily.
You have a function that always inputs an interval (natural numbers in this case), this function returns a result, but is quite expensive on the processor, simulated by sleep in this example:
function calculate($start, $end) {
$result = 0;
for($x=$start;$x<=$end;$x++) {
$result++;
usleep(250000);
}
return $result;
}
In order to be more efficient there is an array of old results, that contains the interval used an the result of the function for that interval:
$oldResults = [
['s'=>1, 'e'=>2, 'r' => 1],
['s'=>2, 'e'=>6, 'r' => 4],
['s'=>4, 'e'=>7, 'r' => 3]
];
If I call calculate(1,10) the function should be able to calculate new intervals based on old results and accumulate them, In this particular case it should take the old result from 1 to 2 add that to the old result from 2 to 6 and do a new calculate(6,10) and add that too. Take in consideration that the function ignores the old saved interval from 4 to 7 since it was more convenient to use 2-6.
This is a visual representation of the problem:
Of course in this example, calculate() is quite simple and you can just find particular ways to solve this problem around it, but in the real code calculate() is complex and the only thing I know is that calculate(n0,n3)==calculate(n0,n1)+calculate(n1,n2)+calculate(n2,n3).
I cannot find a way to solve the reuse of the old data without using a bunch of IF and foreach, I'm sure there is a more elegant approach to solve this.
You can play with the code here.
Note: I'm using PHP but I can read JS, Pyton, C and similar languages.
if you are certain that calculate(n0,n3)==calculate(n0,n1)+calculate(n1,n2)+calculate(n2,n3), then it seems to me that one approach might simply be to establish a database cache.
you can pre-calculate each discrete interval, and store its result in a record.
$start = 0;
$end = 1000;
for($i=1;$i<=$end;$i++) {
$result = calculate($start, $i);
$sql = "INSERT INTO calculated_cache (start, end, result) VALUES ($start,$i,$result)";
// execute statement via whatever dbms api
$start++;
}
now whenever new requests come in, a database lookup should be significantly faster. note you may need to tinker with my boundary cases in this rough example.
function fetch_calculated_cache($start, $end) {
$sql = "
SELECT SUM(result)
FROM calculated_cache
WHERE (start BETWEEN $start AND $end)
AND (end BETWEEN $start AND $end)
";
$result = // whatever dbms api you chose
return $result;
}
there are a couple obvious considerations such as:
cache invalidation. how often will the results of your calculate function change? you'll need to repopulate the database then.
how many intervals do you want to store? in my example, I arbitrarily picked 1000
will you ever need to retrieve non-sequential interval results? you'll need to apply the above procedure in chunks.
i wrote this:
function findFittingFromCache($from, $to, $cache){
//length for measuring usefulnes of chunk from cache (now 0.1 means 10% percent of total length)
$totalLength = abs($to - $from);
$candidates = array_filter($cache, function($val) use ($from, $to, $totalLength){
$chunkLength = abs($val['e'] - $val['s']);
if($from <= $val['s'] && $to >= $val['e'] && ($chunkLength/$totalLength > 0.1)){
return true;
}
return false;
});
//sorting to have non-decremental values of $x['s']
usort($candidates, function($a, $b){ return $a['s'] - $b['s']; });
$flowCheck = $from;
$needToCompute = array();
foreach($candidates as $key => $val){
if($val['s'] < $flowCheck){
//already using something with this interval
unset($candidates[$key]);
} else {
if($val['s'] > $flowCheck){
//save what will be needed to compute
$needToCompute[] = array('s'=>$flowCheck, 'e'=>$val['s']);
}
//increase starting position for next loop
$flowCheck = $val['e'];
}
}
//rest needs to be computed as well
if($flowCheck < $to){
$needToCompute[] = array('s'=>$flowCheck, 'e'=>$to);
}
return array("computed"=>$candidates, "missing"=>$needToCompute);
}
It is function which returns you two arrays, one "computed" holds found already computed pieces, second "missing" holds gaps between them which must be computed yet.
inside function there is 0.1 threshold, which disqualifies chunks shorter than 10% of total searched length, you can rewrite function to send threshold as parameter, or ommit it completely.
i presume results will be stored and after computing added into cache ($oldResults), which might be of any form (for example database as Jeff Puckett suggested). Do not forget to add all computed chunks and whole seeked length into cache.
I am sorry but i can't find a way without cycles and ifs
Working demo:
link
I have a piece of code which will select x number of days into the future and print it out.
I'm then trying to select data from those timestamps, and print out accordingly:
Below I am selecting the number of days in the future it should loop ($max) and how many rows/data there is ($data["cnt"])
$stmt=$dbh->prepare("select round((expire - unix_timestamp()) / 86400) as days, count(*) as cnt from xeon_users_rented WHERE user_by=:username group by days;");
$stmt->bindParam(":username",$userdata['username']);
$stmt->execute();
$data=$stmt->fetchAll();
$max = max(array_map(function($d){
return $d['days'];
}, $data));
$expireData = array();
I then loop through x number of days in the future and print it out: (Let's say that $x is = 10)
for($x = 0; $x <= $max; $x++){
if ($data[$x]["cnt"] > 0){
$expireData[] = $data[$x]["cnt"];
}else{
$expireData[] = 0;
}
$stamp = strtotime('+'.$x.' day', time());
$expireDays[] = date("Y/m/d", $stamp);
}
I then print out the days data and the data:
<?php echo implode("', '", $expireDays); ?>
<?php echo implode("', '", $expireData); ?>
Which gives me:
'2014/11/05', '2014/11/06', '2014/11/07', '2014/11/08', '2014/11/09', '2014/11/10', '2014/11/11', '2014/11/12', '2014/11/13', '2014/11/14', '2014/11/15'
and (where each digit represent a value for that specific date)
2,8,0,0,0,0,0,0,0,0
So far so good. The only problem here is, that the data (2,8,0,0etc.) is not correct. It should for example be:
0,0,2,0,0,0,8,0,0,0
My question is: How can I print out the data, where it matches the timestamp (xeon_users_rented.expire)?
To simplify my answer from before and to answer your question directly "How can I print out the data, where it matches the timestamp"?
You need to first put the unix timestamp of "strtotime('+'.$x.' day', time());" into an array from your original loop. Remove the expiredays[] stuff from that loop.
Then loop through that array and then use array_search for finding any matching indexes in the $data array.
if (found in $data array)
$expireDays[] = $data[array_search position]['cnt'];
else
$expireDays[] = 0;
From what I have gathered in what you are trying to establish, the sql query (for example) returns an array such as:
$data = array(
array("days"=>232975857, "cnt"=> 4),
array("days"=>232975867, "cnt"=> 10),
array("days"=>232976689, "cnt"=> 0),
array("days"=>232976688, "cnt"=> 2)
);
The max in your case is 10. However, please note that your code (below):
$max = max(array_map(function($d){
return $d['days'];
}, $data));
could return a lot of PHP E_NOTICE errors and be slow because you are working out a maximum from the unix_timestamp at that stage which is for example 232975867 (far too many loops I suspect that you need). The max should be worked out in the following way I suspect:
$max = count($data);
In my case (from my data example example) this will return something like 4 for which your for loop code will need to reference "<" not "<=". To optimise this I would actually put straight into the for loop "...; $x < count($data); ...;" unless of course you need the $max later.
Here is a big issue for me. I don't see where currently you have any correlation between the $stamp variable and the "days" column from your sql statement. Perhaps I have not seen enough information from you to fully understand or I am interpreting your question incorrectly but your sql for one will not necessarily return the same dates as the stamp variable will calculate and will not certainly return a cnt of 0 for any dates that do not exist in that table. This is why:
if ($data[$x]["cnt"] > 0){
part of the section is unnecessary and possibly incorrect.
To answer your question why do you get "2,8,0,0,0,0...." instead of the order you expected is because the sql does not return 0 cnt values as quite simply the date does not exist in it's table and your implode still returns '0's appended as you forcibly added the 0's afterwords with the line:
$expireData[] = 0;
First of all, you need to fill your data (or re-write your data to contain cnt of '0's in the correct array places). You can achieve this from the sql level with a subquery that ensures missing dates are contained and then a cnt value of 0 is enforced. I'll leave this to you to work out however another way (via PHP) is to do the following (pseudo code):
place each 'stamps' (in unix format) in array from previous loop
forloop $i through $stamps
array_search $stamps against $data['days']
if (found)
$expireDays[] = $data[array_search position]['cnt'];
else
$expireDays[] = 0;
This means that you remove the $expireDays from your first loop.
Finally, perhaps I have misunderstood and that your 'days' column shouldn't match your $stamp dates as those dates are in the future and your 'days' columns are in the past. In this case, your only option is to adjust your sql statement to forcibly include dates that are missing (between a certain date range)
Good luck.
I am implementing a system at the moment where it needs to allocate a number in a certain range to a person, but not use any number that has been used before.
Keep in mind, both the number range and exclusion list are both going to be quite large.
Initially, I thought doing something like this would be best:
<?php
$start = 1;
$end = 199999;
$excluded = array(4,6,7,8,9,34);
$found = FALSE;
while (!$found) {
$rand = mt_rand($start,$end);
if (!in_array($rand,$excluded)) {
$found = TRUE;
}
}
?>
But I don't think this is ideal, there is the possibility of an infinite loop (or it taking a very long time / timing out the script).
I also thought about generating an array of all the numbers I needed, but surely a massive array would be worse? Also doing an array diff on 2 massive arrays would surely take a long time too?
Something like this:
<?php
$start = 1;
$end = 199999;
$allnums = range($start,$end);
$excluded = array(4,6,7,8,9,34);
$searcharray = array_diff($allnums,$excluded);
$rand = array_rand($searcharray);
?>
So, my question would be which would be a better option? And is there another (better) way of doing this that someone has used before?
Array's holding large amounts of data will use up a lot of memory, can you not use a database to hold these numbers in? That's generally what they are designed for.
I'm working on a PHP-written html calendar that writes each day of the month inside a while loop.
Each day of the month is inside a pair of tags and certain days need a title attribute in the tag. Those days will be obtained from the MySQL db and stored in an array like this: $array($day_number=>$quantity).
An example array might be: (3=>5, 12=>4, 15=>6, 22=>10, 27=>2, 31=>4). The array would only contain keys for days where the quantity is not zero.
I can think of two ways to do this. I'm wondering which one is more efficient, or if there is another, best way.
Option 1.) Check the array at each iteration of the html-creating loop to see if it contains the corresponding day. If so, add the appropriate title attribute to the tag. So I would be using something like:
$day = 1;
while($day < 31) {
if(array_key_exists($day,$array)) {
echo "<td title=\"$array['$day'] spots available\">$day</td>";
}
else echo "<td title\"No spots available for this date\">$day</td>";
$day++;
}
2.) Use loop to put entire calendar into a string variable, then use string functions to insert special title attributes.
$day = 1;
while($day < 31) {
$month .= "<td>$day</td>";
$day++;
}
foreach($array as $day_number=>$quantity) {
$month = str_replace("<td>$day_number</td>","<td title=\"$quantity spots available\">$day_number</td>",$month)
}
In this application, either method will be done very quickly but my question is more general. Is it better to use string functions after the loop that creates the basic html, or to checking/processing at each iteration? Or is there a third, best way?
I have learned PHP entirely by myself using internet resources so I have no idea how bad my coding may be. Any help is appreciated.
Thank you.
Here's another solution:
$day = 1;
$strings = array();
while($day < 31) {
if (array_key_exists($day, $array)) {
$strings[$day] = $array['$day'] . " spots available";
} else {
$strings[$day] = "No spots available for this date";
}
$day += 1;
}
foreach ($strings as $day => $string) {
echo '<td title="' . $string . '">' . $day . '</td>';
}
What is so different about it? Well, fist of all, it's likely going to be slower than your solution since I'm looping 31 times, twice! But this example is so trivial that performance is not your main concern.
Your main concern is writing code that is so simple anyone can understand it.
PHP code gets very complicated if you have lots of HTML printing going on. Generally what you want to do is make some sort of model (adhoc or systematic) that collects all your data, and only prints it to HTML as the very last step.
Learn to separate the data-collection and model generation step from the HTML printing step. This may seem like overkill and a waste of CPU power and memory and what not, but what is more expensive: your time and sanity or some server in a hot room somewhere? ;)
Your choice to have a sparse array of only the days that have spots available is already an optimization. And premature optimization is the mother of all evil. Think about the easiest way to solve your problem, build that, it's likely going to be fast enough anyway.