Hi Elaine,

I declared the centroid of a tyrosine residue's ring by first selecting its ring members & then using the command: define centroid sel radius 0.5

Next, when I try to find the distance between the centroid, I get an error whose screenshot I have attached with the email. The command that I am using to find the distance are:

dist #1.1 #1.2 (here the distance is being calculated between two centroids)

Please help