Find combined mean and variance of two series | Function to find mean of series . ; Function to find the standard deviation of series . ; Function to find combined variance of two different series . ; mean1 and mean2 are the mean of two arrays . ; sd1 and sd2 are the standard deviation of two array . ; combinedMean is variable to store the combined mean of both array . ; d1_square and d2_square are the combined mean deviation . ; combinedVar is variable to store combined variance of both array . ; Driver Code ; Function call to combined mean .
< ? php function mean ( $ arr , $ n ) { $ sum = 0 ; for ( $ i = 0 ; $ i < $ n ; $ i ++ ) $ sum = $ sum + $ arr [ $ i ] ; $ mean = ( float ) ( $ sum / $ n ) ; return $ mean ; } function sd ( $ arr , $ n ) { $ sum = 0 ; for ( $ i = 0 ; $ i < $ n ; $ i ++ ) $ sum = $ sum + ( $ arr [ $ i ] - mean ( $ arr , $ n ) ) * ( $ arr [ $ i ] - mean ( $ arr , $ n ) ) ; $ sdd = $ sum / $ n ; return $ sdd ; } function combinedVariance ( $ arr1 , $ arr2 , $ n , $ m ) { $ mean1 = mean ( $ arr1 , $ n ) ; $ mean2 = mean ( $ arr2 , $ m ) ; echo ( " Mean1 : ▁ " . round ( $ mean1 , 2 ) . " " ▁ . STRNEWLINE TABSYMBOL TABSYMBOL " mean2 : " $ sd1 = sd ( $ arr1 , $ n ) ; $ sd2 = sd ( $ arr2 , $ m ) ; echo ( " StandardDeviation1 : " ▁ . ▁ round ( $ sd1 , ▁ 2 ) ▁ . ▁ " " STRNEWLINE TABSYMBOL TABSYMBOL . ▁ " StandardDeviation2 : " $ combinedMean = ( float ) ( $ n * $ mean1 + $ m * $ mean2 ) / ( $ n + $ m ) ; echo ( " Combined Mean : " round ( $ combinedMean , 2 ) ) ; $ d1_square = ( $ mean1 - $ combinedMean ) * ( $ mean1 - $ combinedMean ) ; $ d2_square = ( $ mean2 - $ combinedMean ) * ( $ mean2 - $ combinedMean ) ; echo ( " d1 square : " ▁ . ▁ round ( $ d1 _ square , ▁ 2 ) ▁ . ▁ " " STRNEWLINE TABSYMBOL TABSYMBOL . ▁ " d2_square : " $ combinedVar = ( $ n * ( $ sd1 + $ d1_square ) + $ m * ( $ sd2 + $ d2_square ) ) / ( $ n + $ m ) ; return $ combinedVar ; } $ arr1 = array ( 23 , 45 , 34 , 78 , 12 , 76 , 34 ) ; $ arr2 = array ( 65 , 67 , 34 , 23 , 45 ) ; $ n = sizeof ( $ arr1 ) ; $ m = sizeof ( $ arr2 ) ; echo ( " Combined Variance : " . round ( combinedVariance ( $ arr1 , $ arr2 , $ n , $ m ) , 2 ) ) ; ? >