[ferret_users] zero values to NaN

[Atul Srivastava <atul.ecc@xxxxxxxxx>]

Dear ferret users I am new in ferret please tell me how I can set zero values in the data sets to NaN values. Regarding this I am using this command but it does not work properly.

let uvels=uvel[x=40E:110E,y=20S:30N,z=1:500]

let nan = "NaN"

let uvelsn=IF uvels eq 0 THEN nan