x1 covariance:
0.09 1.7e-33 2.8e-33
1.7e-33 0.09 2.6e-17
2.8e-33 2.6e-17 0.01
x2 covariance:
0.13 1.2e-18 6.1e-19
1.2e-18 0.17 0.02
6.1e-19 0.02 0.02
x3 covariance:
0.17 8.6e-18 2.7e-18
8.6e-18 0.37 0.06
2.7e-18 0.06 0.03