关于PHP求多项式导数的函数代码

 ?php function getDerivativeByFormulaAndXDATA($formula, $x_data){ $xArray = explode( + , $formula); $Derivative = 0; foreach ($xArray as $x_record) { $tmpArray = explode( x^ , $x_record); if(count($tmpArray) == 2){ $coefficient = $tmpArray[0]== ?1:$tmpArray[0]; $exp = $tmpArray[1]; //constant else { $coefficient = $tmpArray[0]; $exp = 0; $Derivative += $coefficient*$exp*pow($x_data,$exp-1); return $Derivative; function getValueByFormulaAndXDATA($formula, $x_data){ $xArray = explode( + , $formula); $y_data = 0; foreach ($xArray as $x_record) { $tmpArray = explode( x^ , $x_record); if(count($tmpArray) == 2){ $coefficient = $tmpArray[0]== ?1:$tmpArray[0]; $exp = $tmpArray[1]; //constant else { $coefficient = $tmpArray[0]; $exp = 0; $y_data += $coefficient*pow($x_data,$exp); return $y_data; function getMaxDerivativeByFormulaAndXDATAS($formula, $x_datas, $matchs){ $derivatives = array(); $max_derivative = 0; foreach ($x_datas as $x_data) { $derivative = getDerivativeByFormulaAndXDATA($formula, $x_data); $derivatives[$x_data] = $derivative; $max_derivative = $max_derivative =abs($derivative)?$max_derivative:abs($derivative); //printf( x=%f, derivative=%f /n ,$x_data, $derivative); $matchs = array(); foreach ($derivatives as $x_data= $derivative) { if(abs($derivative) == $max_derivative){ $matchs[] = $x_data; printf( max derivative=%f/n ,$max_derivative); foreach ($matchs as $x_match) { printf( derivative=%f when x=%f/n ,$derivatives[$x_match], $x_match); //notice the format of formula: ax^b if b=0 could omit except coefficient a, if a=1 could omit coefficient $formula = x^2+2x^1+1 print The formula is $formula /n //printf( Derivative of 2 is %f /n ,getDerivativeByFormulaAndXDATA($formula, 3.2)); //print getValueByFormulaAndXDATA($formula, 3.2). /n $sampleData = array(-12,-11,-10,-9,-8,-7,-6,-5,-4,-3,-2,-1,1,2,3,4,5,6,7,8,9,10,11,12); foreach ($sampleData as $x_data) { $str.=$x_data. , print sample x html' target='_blank'>values: $str /n getMaxDerivativeByFormulaAndXDATAS($formula, $sampleData, $matchs). /n ? 

the output will be:
sample x values: -12, -11, -10, -9, -8, -7, -6, -5, -4, -3, -2, -1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
max derivative=26.000000
derivative=26.000000 when x=12.000000

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