import mir.math.sum: Summation;
import mir.ndslice.slice: sliced;
import mir.test: shouldApprox;

auto x = [  0.0,   1.0,   1.5,  2.0,  3.5, 4.25,
            2.0,   7.5,   5.0,  1.0,  1.5,  0.0].sliced;
auto y = [-0.75,   6.0, -0.25, 8.25, 5.75,  3.5,
           9.25, -0.75,   2.5, 1.25,   -1, 2.25].sliced;

CorrelationAccumulator!(double, CorrelationAlgo.naive, Summation.naive) v;
v.put(x, y);

v.covariance(true).shouldApprox == 82.25 / 12 - (29.25 * 36) / (12 * 12);
v.covariance(false).shouldApprox == 82.25 / 11 - (29.25 * 36) / (12 * 12) * (12.0 / 11);

v.correlation.shouldApprox == -0.0623684;

v.put(4.0, 3.0);
v.covariance(true).shouldApprox == 94.25 / 13 - (33.25 * 39) / (13 * 13);
v.covariance(false).shouldApprox == 94.25 / 12 - (33.25 * 39) / (13 * 13) * (13.0 / 12);

v.correlation.shouldApprox == -0.0611234;