class interpolators {

////////////////////////////////////////////////////////////////
///
///	        some statistical functons.
///
////////////////////////////////////////////////////////////////
function stat_mean ($data) {
// calculates mean
return (array_sum($data) / count($data));
}

function stat_median ($data) {
// calculates median
sort ($data);
$elements = count ($data);
if (($elements % 2) == 0) {
$i = $elements / 2;
return (($data[$i - 1] + $data[$i]) / 2);
} else {
$i = ($elements - 1) / 2;
return $data[$i];
}
}

function stat_range ($data) {
// calculates range
return (max($data) - min($data));
}

function stat_var ($data) {
// calculates sample variance
$n = count ($data);
$mean = stat_mean ($data);
$sum = 0;
foreach ($data as $element) {
$sum += pow (($element - $mean), 2);
}
return ($sum / ($n - 1));
}

function stat_varp ($data) {
// calculates population variance
$n = count ($data);
$mean = stat_mean ($data);
$sum = 0;
foreach ($data as $element) {
$sum += pow (($element - $mean), 2);
}
return ($sum / $n);
}

function stat_stdev ($data) {
// calculates sample standard deviation
return sqrt (stat_var($data));
}

function stat_stdevp ($data) {
// calculates population standard deviation
return sqrt (stat_varp($data));
}
/////////////////////////end statistical functions///////////////////////////
/////////////should make it in seperate class, i think///////////////////////
/////////////////////////////////////////////////////////////////////////////





/////////////////////////////////////////////////////////////////////////////
//function which returns year and month according to:
//if it is the first day on the month, it returns the current year and month,
//otherwise it returns next month with according year
/////////////////////////////////////////////////////////////////////////////	
	function firstFullYearMonth($dateString)
		{
		try {
			$firstDate = new DateTime($dateString);			
		} 
		catch (Exception $e) {
			echo $e->getMessage();
		exit(1);
		}
				$firstDate= new DateTime($dateString);				
				$currentDay=(int) $firstDate->format('d');
				$currentMonth=(int) $firstDate->format('m');
				$currentYear=(int) $firstDate->format('y');
				$prevMonth = (int) date("m", mktime(0, 0, 0, $currentMonth, $currentDay-1, $currentYear));

				if ($currentMonth>$prevMonth)
					{
					$firstDay=date("Y-m", mktime(0, 0, 0, $currentMonth, $currentDay, $currentYear));	
					}
				else
					{
					$firstDay = date("Y-m", mktime(0, 0, 0, $currentMonth+1, 1, $currentYear));
					}	
		return $firstDay;
	}

/////////////////////////////////////////////////////////////////////////////
//function which returns year and month according to:
//if the date consists of the last day on the month, it returns the current year and month,
//otherwise it returns previous month with according year
/////////////////////////////////////////////////////////////////////////////	
	function lastFullYearMonth($dateString)
		{
		try {
			$firstDate = new DateTime($dateString);			
		} 
		catch (Exception $e) {
			echo $e->getMessage();
		exit(1);
		}
				$firstDate= new DateTime($dateString);				
				$currentDay=(int) $firstDate->format('d');
				$currentMonth=(int) $firstDate->format('m');
				$currentYear=(int) $firstDate->format('y');
				$nextMonth = (int) date("m", mktime(0, 0, 0, $currentMonth, $currentDay+1, $currentYear));

				if ($currentMonth<$nextMonth)
					{
					$lastDay = date("Y-m", mktime(0, 0, 0, $currentMonth, $currentDay, $currentYear));			
					}
				else
					{
					$lastDay = date("Y-m", mktime(0, 0, 0, $currentMonth, 0, $currentYear)); // 0tā diena - iepriekšējā mēneša pēdējā diena.
					}
		return $lastDay;
	}
	
/////////////////////////////////////////////////////////////////////////////
//Function interpolates values from 2d array where measurement date is in the first 
//dimension and measured value in the second dimension.
//Function returns 2d array with interpolated values for each date between measurements
/////////////////////////////////////////////////////////////////////////////		
	function interpolate($arrays)
	{
		
		$oldDate=$this->firstValDate($arrays);
		$oldVal=$this->firstValVal($arrays);
		
		next($arrays);
		
		foreach ($arrays as $key=>$tmpArray)
			{
			$ii=0;
			foreach ($tmpArray as $value)
				{
					$keys= new DateTime($key);		//try different date formats
					$keys=$keys->format("Y-m-d");   //compare with standart
					if ($keys!=$oldDate)
						{
						$datums=$keys;
						$vertiba=$value;
						
						$datetimeOld	 = new DateTime($oldDate);
						$datetimeCurrent = new DateTime($datums);
						
						$lastForInt = strtotime($oldDate);
						$firstForInt = strtotime($datums);
						
						$intervals = round(($firstForInt-$lastForInt)/60/60/24);
						if ($intervals<0)
							{
							echo "Nākošais datums ir senāks par iepriekšējo.\nLaiks parasti iet uz priekšu un nenāk atpakaļ.";
							die;
							}
						//echo $intervals;
						
						$delta=$vertiba-$oldVal;
						$increment = $delta/$intervals;

						if ($intervals>1)
							{			
								for ($i=1;$i<=$intervals;$i++)
								{
									$datetimeOld->modify('+1 day');						//vecajam datumam pieliek vienu dienu klāt
									$currentDay=$datetimeOld->format('Y-m-d');			//pārtaisa datumobjektu uz string
									$interpValue=round($oldVal+$increment*$i,2);		//aprēķina patreizējās dienas vērtību pēc formulas
																						//vecā vērtība plus esošais solis reiz soļa lielums
									$interpBoolText=(($i!=$intervals)?"\ti":"");		//visos soļos atrastajai vērtībai galā būs strings "i",
																						//tas ļauj uzskatāmi redzēt, ka tieši šī vērtība ir interpolēta
									$interpArray[$currentDay][$ii]=$interpValue;
									$ii++;
								}
						$oldDate=$datums;												//definējam nākošo "iepriekšējo" datumu un vērtību
						$oldVal=$vertiba;
							}
						else
							{
							$interpArray[$datums][$ii]=$vertiba;
							$oldDate=$datums;
							$oldVal=$vertiba;
							$ii++;
							}
						
						}
					else
						{
						$interpArray[$key][$ii]=$value;
						$ii++;
						}
				}
			}
			//print_r ($interpArray);
		return $interpArray;
	}


/////////////////////////////////////////////////////////////////////////////
//Returns first key - date value from 2 dimensional associative key array.
//
//
/////////////////////////////////////////////////////////////////////////////
	function firstValDate($arrays)
	{
		foreach ($arrays as $key=>$tempArray)
			{
				return $key;
				break;
			}
	}

/////////////////////////////////////////////////////////////////////////////
//Returns last key - date value from 2 dimensional associative key array.
//
//are there direct way how to get the last key of associative array?
//such loop seems kind of stupid...
/////////////////////////////////////////////////////////////////////////////
	function lastValDate($arrays)
	{
		$i=1;	
		foreach ($arrays as $key=>$tempArray)
			{				
				if ($i==count($arrays))
				{
				return $key;
				break;
				}
				$i++;
			}
	}
	
/////////////////////////////////////////////////////////////////////////////
//Returns first key - date value from 2 dimensional associative key array.
//
//
/////////////////////////////////////////////////////////////////////////////
	function firstValVal($arrays)
	{
		return $arrays[$oldDate=$this->firstValDate($arrays)][0];
		
	}
/////////////////////////////////////////////////////////////////////////////
//Function checks element first two symbols (are they tabs), checks, if the value
//is null or empty and deletes such element.
//
/////////////////////////////////////////////////////////////////////////////		
	function unsetEmpty($arrays)
	{
		$i=0;
		foreach($arrays as $key=>$value) 
			{ 
			$rest = substr($value, 0, 2);
			if(!(is_null($value) || $value=="" || $rest=="\t\t")) 
				{
				$arrayNew[$i]=$value;
				$i++;
				} 
			}
	return $arrayNew;
	}
	
/////////////////////////////////////////////////////////////////////////////
//Function makes 2 dimensional array from string which is formatted by default
//as "date (tab) value". 
//
//should make possibility to divide string in parts and define them (seperator, etc)
//by giving optional parameters.
/////////////////////////////////////////////////////////////////////////////		
	function make2dArrayFromDateValueString($dateValueString)
	{
		$text = str_replace("\r", "", $dateValueString);
		$text = str_replace("\n", "+", $text);
		$text = str_replace(",",".",$text);
		$arrtext = explode("+", $text);
		$arrtext=$this->unsetEmpty($arrtext);

		$i=0;
		foreach($arrtext as $key=>$value)
			{
				$bothValues= explode ("\t",$value);
				$datums=$bothValues[0];
				$vertiba=$bothValues[1];
				$masivs2d[$datums][$i]=$vertiba;
				$i++;
			}
		return $masivs2d;
	}

/////////////////////////////////////////////////////////////////////////////
//Function cuts the months which has unfilled daily mesaured values
//
//
/////////////////////////////////////////////////////////////////////////////		
	function cutInterpolated($arrays)
		{
		$FirstDateFrom2dArray=$this->firstValDate($arrays);
		$LastDateFrom2dArray=$this->lastValDate($arrays);
		$FirstFullYearMonth=$this->firstFullYearMonth($FirstDateFrom2dArray);
		$LastFullYearMonth=$this->lastFullYearMonth($LastDateFrom2dArray);
		$validDayCount=round((strtotime($LastFullYearMonth."-2")-strtotime($FirstFullYearMonth."-01"))/60/60/24)+1;
		
		//echo $validDayCount;
		//echo $FirstFullYearMonth;
		//$LastDateFrom2dArray
		if ($validDayCount>0)
			{
				$i=0;
				foreach ($arrays as $key=>$tmpArray)
				{
					foreach ($tmpArray as $value)
						{
						if (($key>=$FirstFullYearMonth) and ($key<=$LastFullYearMonth))
							{
							$array[$key][$i]=$value;
							$i++;
							}
						}
				}
			}
		return $array;
		}


/////////////////////////////////////////////////////////////////////////////
//create 2d array with year and month in first dimension and respective 
//daily data valuesin seceond
/////////////////////////////////////////////////////////////////////////////			
	function createByYearMonth($arrays)
		{
				$k=0;
				foreach ($arrays as $key=>$tmpArray)
				{
					foreach ($tmpArray as $value)
						{
						$currDate=new datetime($key."-01");
						$Months=(int)$currDate->format("m");						
						if (($oldmonth<$Months) or (($oldmonth==12) and ($Months==1)))					//skatamies, ja nākamais mēnesis, tad ieliekam iekš masīva
								{
								$k=0;
								$gadsMenesis=$currDate->format("Y-").$oldmonth;		
								$paMenesiem[$currDate->format("Y-m")][$k]=$value;								//izdala gadu un pareizo mēnesi masīvam	
								$k++;
								}
							else
								{
								//echo $value;
								$paMenesiem[$currDate->format("Y-m")][$k]=$value;
								$k++;																		
								}	
								$oldmonth=$Months;
							
						}
				}
				//print_r ($paMenesiem);			
		return $paMenesiem;
		}
/////////////////////////////////////////////////////////////////////////////
//create 2d array with year and month in first dimension and statistical values 
//for respective monthly data in second.
//0 - count
//1 - min
//2 - max
//3 - sum
//4 - average
//5 - median
//6 - variance (for sample)
//7 - variance (for population)
//8 - standart deviation (for sample)
//9 - standart deviation (for population)
/////////////////////////////////////////////////////////////////////////////			
	
	function getStatistics($arrays)
		{
		foreach ($arrays as $key=>$tempone) {
				$array[$key]["count"]=count($tempone);
				$array[$key]["min"]=min($tempone);
				$array[$key]["max"]=max($tempone);
				$array[$key]["sum"]=array_sum($tempone);
				$array[$key]["average"]=stat_mean($tempone);
				$array[$key]["median"]=stat_median($tempone);
				$array[$key]["variance"]=stat_var($tempone);
				$array[$key]["variancep"]=stat_varp($tempone);
				$array[$key]["stdev"]=stat_stdev($tempone);
				$array[$key]["stdevp"]=stat_stdevp($tempone);
				}
			return $array;
		}
	
}



$interpolators = new interpolators();	//create interpolator object
$masivStrings=$_POST['tabula']; //get some data (date\tvalue\n(\r)) format
$arrays2d= $interpolators->make2dArrayFromDateValueString($masivStrings); //create from gathered data 2dimensional array
$interpolatedArray = $interpolators->interpolate($arrays2d); 				//interpolate it daily
$cuttedArray=$interpolators->cutInterpolated($interpolatedArray);			//cut end and last month, if it is not started/lasted from beginning/till end
$paMenesiem=$interpolators->createByYearMonth($cuttedArray);				//sepereate values for each month
$statistika=$interpolators->getStatistics($paMenesiem);						//get some monthly statistics