inv
Matrix inverse
inv x inv[x]
Returns the inverse of non-singular float matrix x.
q)a:3 3#2 4 8 3 5 6 0 7 1f
q)inv a
-0.4512195 0.6341463 -0.195122
-0.03658537 0.02439024 0.1463415
0.2560976 -0.1707317 -0.02439024
q)a mmu inv a
1 2.220446e-16 -2.775558e-17
0 1 5.551115e-17
0 0 1
q)1=a mmu inv a
100b
010b
001b
lsq solves a normal equations matrix via Cholesky decomposition – solving systems is more robust than matrix inversion and multiplication.
Since V3.6 2017.09.26 inv uses LU decomposition.
Previously it used Cholesky decomposition as well.