2019 formula from 2018 document:
This formula can be cutâ€™npasted into xmgrace to convert the x-axist from table angle to lamda in nm:
320+1*(sqrt((1.1547*sin(g3.s10.x deg)+0.5)^2+0.75)-1.635)^-1+0.2*(sqrt((1.1547*sin(g3.s10.x deg)+0.5)^2+0.75)-1.635)^-2+0.19*(sqrt((1.1547*sin(g3.s10.x deg)+0.5)^2+0.75)-1.635)^-3
Looks like QT-grace cannot take the deg to make angle calculation on sin (angle) as degrees. Saw that on the grace forum in a post from the author (Evgeny). Had to do the *pi/180 in windows. Further testing likely needed however.