public static double var ( int [ ] x ) { if ( x . length < 2 ) { throw new IllegalArgumentException ( "Array length is less than 2." ) ; } double sum = 0.0 ; double sumsq = 0.0 ; for ( int xi : x ) { sum += xi ; sumsq += xi * xi ; } int n = x . length - 1 ; return sumsq / n - ( sum / x . length ) * ( sum / n ) ; }
Returns the variance of an array .