Re: [ferret_users] local minima and maxima computation

[Russ Fiedler <russell.fiedler@xxxxxxxx>]

Hi,

I think Gopal really needs the @WEQ transformation unless he's only ever
interested in a 1D time series.


http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/variables-xpressions/XPRESSIONS#_VPINDEXENTRY_532

The third and fourth examples show how to extract the values of a
variable at another's maxima

Essentially you create a third variable which has its maxima  (say in
time) subtracted from it. Locate the zero of this new variable and
construct an integrating kernel.

e.g.

let zero_chl_max = chl - chl[t=@max]
let kernel = zero_chl_max[t=@WEQ:0]
let integrand_salt = salt*kernel
let integrand_temp = temp*kernel

let salt_at_chl_max = integrand_salt[t=@sum]
let temp_at_chl_max = integrand_temp[t=@sum]

Russ


On Mon, 2013-04-29 at 08:25 -0700, Steve Hankin wrote:
> See @LOC transformation:
> http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/variables-xpressions/XPRESSIONS#_VPINDEXENTRY_528
> 
> On 4/27/2013 1:55 AM, Gopal Mondal wrote:
> 
> > Dear all
> > 
> >             I am facing same type of problem. Suppose sal, temp,
> > chlorofil, all three parameters are varying with time. Time is in X
> > axis . How can I extract the value of temp and sal for max chlorofil
> > from the data file.Pls help me any one. Thank s to everybody.
> > 
> > Gopal Mondal
> > 
> > 
> > 
> > On Fri, Apr 26, 2013 at 6:54 PM, Andre Paim <paim.oceano@xxxxxxxxx>
> > wrote:
> >         Dear Nagarjuna, 
> >         
> >         
> >         I am not sure if I understood exactly what you want, but
> >         have you tried the @min and @max?
> >         
> >         
> >         If you want to find the min and max at each point along a
> >         time series, all you have to do is:
> >         (Assuming your variable is the temperature)
> >         
> >         
> >         let temp_max = temperature[L=@max]
> >         let temp_min = temperature[L=@min]
> >         
> >         
> >         
> >         In the same fashion, if you want to find the min and max
> >         along the depth, all you have to do is substitute the "L"
> >         for "K", and so on.
> >         
> >         
> >         let temp_max = temperature[K=@max]
> >         let temp_min = temperature[K=@min]
> >         
> >         
> >         
> >         
> >         
> >         Was that your question?
> >         Regards,
> >         
> >         
> >         
> >         André Paim
> >         
> >         
> >         
> >         
> >         On 26 April 2013 04:01, Nagarjuna Rao <dnrao.au@xxxxxxxxx>
> >         wrote:
> >                 Dear All,
> >                 
> >                 
> >                 
> >                   Does ferret has any function to compute the
> >                 relative minima and maxima's of a variable at each
> >                 grid.
> >                 
> >                 
> >                 
> >                 Thanks in advance for any help,
> >                 
> >                 D.Nagarjuna Rao.
> >                 
> >         
> >         
> > 
> > 
>