[ferret_users]if else statement on negative values

[jean li <xgeast@xxxxxxxxx>]

Hi All:

 

I am trying to use the "if else" statement to set the lower limit of negative values.

However, the script below is not working. u_ave_1 still has the value below -20. It's supposed to work and had worked before. I don't quite understand why.     

 

let u_ave_1 = if u_ave[d=1] lt (-20) then (-20) else u_ave[d=1]

 

Thanks in advance for your help!

 

Zhen