Compute the rotation matrix d(pi/2) used in rotating data expressed in spherical harmonics.
`dj` = djpi2 (`lmax`)
dj
: float, dimension (lmax
+1, lmax
+1, lmax
+1)
: The rotation matrix dj(pi/2).
lmax
: integer
: The maximum spherical harmonic degree of the spherical harmonic rotation.
djpi2
will calculate the rotation matrix d_{mM}^j (pi/2)
that is used in rotating spherical harmonics in the routines SHRotateRealCoef
and SHRotateCoef
.
This routine is based on code originally written by Guy Masters.