我的矩阵：
>mat
[,1] [,2] [,3] [,4]
[1,] 886 108 324 468
[2,] 280 820 783 475
[3,] 219 235 385 578
[4,] 843 672 594 74
> solve(mat) %*% mat
[,1] [,2] [,3] [,4]
[1,] 1.000000e+00 7.105427e-15 1.243450e-14 1.509903e-14
[2,] 0.000000e+00 1.000000e+00 -2.842171e-14 1.953993e-14
[3,] -2.842171e-14 2.842171e-14 1.000000e+00 -3.552714e-14
[4,] 0.000000e+00 -1.421085e-14 -7.105427e-15 1.000000e+00