variance method
Returns the variance of the numbers in array
in the region ixstart, ixend
(ixend exclusive): variance = mean(x**2) - (mean(x))**2
ixstart
and ixend
may be null, equivalent to the left/rightmost index.
Implementation
static double variance(Float64List array, int ixstart, int ixend) {
if (ixstart == null) ixstart = 0;
if (ixend == null) ixend = array.length - 1;
double mean = meanValue(array, ixstart, ixend);
double variance = 0.0;
double value;
for (int i = ixstart; i < ixend; i++) {
value = array[i];
variance += (value - mean) * (value - mean);
}
variance /= ixend - ixstart + 1;
return variance;
}