Re: [ferret_users] shuffle or how to permute randomly elements

[Andrew Wittenberg <Andrew.Wittenberg@xxxxxxxx>]

Hi Patrick,

To shuffle a time series, simply sample your vector with indices that sort
a random array:

   let a_shuffle = samplel(a,sortl(randu(a)))

An example with multiple shuffles:

   let a = tsequence({100,500,600,20,90,4})
   let seeds = {101,102,103}
   let a_shuffle = samplel(a,sortl(randu(tcat(seed,a[l=2:`a,r=lsize`]))))
   rep/name=s/range=1:`seeds,r=isize` (let seed = seeds[i=`s`]; list a_shuffle)

Andrew

On Tue, 25 Jan 2011, Patrick.Brockmann@xxxxxx wrote:

> Hi all,
>
> I have coded a ferret script where 2 variables are
> co-plotted with coloring samples with their latitudes.
>
> It can be easilly achieved with the script polymark.
> yes? go polymark
> polygon/over/nolab/key/lev=(-90,90,10)/pal=centered/nolab/fill
> w1,w2,w3,circle,0.5
> No problem there. See 1st figure attached.
>
> But as I worked from 2D variables, when I vectorize them,
> I conserve their underlaying grid.
>
> For now, I have done this using an external call to python/numpy
>
> yes? go shuffle 10
> yes? list shuffle
>             VARIABLE : SHUFFLE
>             FILENAME : shuffle.txt
>             SUBSET   : 10 points (X)
> 1    /  1:   3.00
> 2    /  2:  10.00
> 3    /  3:   8.00
> 4    /  4:   4.00
> 5    /  5:   7.00
> 6    /  6:   6.00
> 7    /  7:   5.00
> 8    /  8:   1.00
> 9    /  9:   2.00
> 10   / 10:   9.00
>
> Applying this shuffle to my samples with the
> ferret samplei(v1, shuffle) gives me what I was
> expecting (independant sample over their latitudes).
> yes? go polymark
> polygon/over/nolab/key/lev=(-90,90,10)/pal=centered/nolab/fill
> samplei(w1,shuffle),samplei(w2,shuffle),samplei(w3,shuffle),circle,0.5
> See fig2 attached.
>
> I am wondering if a shuffle function could be added to ferret ?
> Any news to share about link between python and ferret ?
>
>
> Patrick