Re: maximum vector length

[<Russell.Fiedler@xxxxxxxxxxxxxxx>]

> From poulsen@essc.PSU.EDU Tue Jan  6 05:40:54 1998
> From: Christopher Poulsen <poulsen@essc.PSU.EDU>
> Date: Mon, 5 Jan 1998 13:36:49 -0500 (EST)
> To: ferret_users@ferret.wrc.noaa.gov
> Subject: maximum vector length
> 
> 
> 
> Hello,
> 
> Does anyone know of an easy way to limit the maximum length of vectors?
> For example, I want every velocity over 20 m/s to be an equal length.
> 
> Thanks,
> Chris
> 
Chris,

Actually, I think that you want the speed (not velocity components) to be
limited to 20 m/s. So, assuming we have u and v in m/s on a grid i=1:10, j=1:10

set region/i=1:10/j=1:10
let speed=(u^2 + v^2)^0.5 
let ul=if(speed gt 20) then u*20/speed else u
let vl=if(speed gt 20) then v*20/speed else v
vector ul,vl

! As a check
let newspeed=(ul^2 + vl^2)^0.5
list speed[i=@max,j=@max],newspeed[i=@max,j=@max]


Cheers,
Russ Fiedler