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Calculate SD
this simple program will calculate the SD(standard deviation) for the given input.
public class StandardDeviation{
public static double mean ( double[] data )
{
double mean = 0;
final int n = data.length;
if ( n < 2 )
return Double.NaN;
for ( int i=0; i<n; i++ )
mean += data[i];
mean /= n;
double sum = 0;
for ( int i=0; i<n; i++ )
{
final double v = data[i] - mean;
sum += v * v;
}
return Math.sqrt( sum / ( n - 1 ) );
}
public static double sd ( double[] data ){
final int n = data.length;
if ( n < 2 )
return Double.NaN;
double avg = data[0];
double sum = 0;
for ( int i = 1; i < data.length; i++ )
{
double newavg = avg + ( data[i] - avg ) / ( i + 1 );
sum += ( data[i] - avg ) * ( data [i] -newavg ) ;
avg = newavg;
}
return Math.sqrt( sum / ( n - 1 ) );
}
public static void main ( String[] args )
{
double[] data = { 10, 100 , 50};
System.out.println(mean(data));
System.out.println(sd (data));
}
}
Source at <a href="http://ncalculators.com/statistics/mean-standard-deviation-calculator.htm">Standard Deviation Calculator</a>
