[ncl-talk] question about sorting

[Marston Johnston]

Hi,

I just tested your example and dim_pqsort_n is what you need but if I understand what you want is for the rows to be sorted and not the columns:

x = (/ (/2015,1,1/),(/2016,2,1/),(/1981,1,2/),(/1982,1,0/),(/1981,0,2/)/)
write_matrix (x, "14I6", False) ; prints x as is
y = dim_pqsort_n(x,2,0)  ; This sorts x in place using the 0th dim and returns the indices, but x will now be sorted since you chose 2: in ascending order.
write_matrix (x, "14I6", False) .


2015     1     1
2016     2     1
1981     1     2
1982     1     0
1981     0     2


  1981     0     0
  1981     1     1
  1982     1     1
  2015     1     2
  2016     2     2

But this solution sorts even the columns. Another way to do this but a bit more memory intensive and keeping the column integrity:

x = (/ (/2015,1,1/),(/2016,2,1/),(/1981,1,2/),(/1982,1,0/),(/1981,0,2/)/)
  zz = x*0 ; Bins for for the sorted results
  write_matrix (x, "14I6", False)
  y = dim_pqsort_n(x,1,0) ; !!!!!!!!!! Do not sort x inplace here!!!!!

z = y(:,0)

  do n = 0,dimsizes(z) - 1
    zz(n,:) = x(z(n),:)
  end do
 write_matrix (zz, "14I6", False)

2015     1     1
  2016     2     1
  1981     1     2
  1982     1     0
  1981     0     2


  1981     0     2
  1981     1     2
  1982     1     0
  2015     1     1
  2016     2     1

Which I think is what you want. Since 1981 occurs twice, the sorting used the next column over for the sorting. So be careful if there are duplicates in col 0.

/M

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Marston S. Ward, PhD
Department of Earth Sciences
University of Gothenburg, Sweden
Email: marston.johnston at gu.se
SkypeID: marston.johnston 
Phone: +46-31-7864901 
Only the fruitful thing is true!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

On 2017-09-14, 15:35, "Damjan Jelić" <damjan.jelic at fmf.uni-lj.si> wrote:

    Yes, i finaly managed to do it, i hope it works correctly :)
    Thanx for suggestions. On the end one must use dim_pqsort_n.
    
    Have a nice day!
    Sincerely,
    Damjan
    
    14-09-2017 15:10, je Marston Johnston napisal
    > Hi,
    > 
    > From the example I sent, you will get a set of indices that will sort
    > the first dim AND will also apply to the other dims of your example
    > array.
    > Then you can simply copy the old array into a new array using the
    > sorted indices /untested/ ar_sort = ar_unsort(ip,ip,ip), where ip is
    > the indices returned from dim_pqsort.
    > 
    > /M
    > 
    > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    > Marston S. Ward, PhD
    > Department of Earth Sciences
    > University of Gothenburg, Sweden
    > Email: marston.johnston at gu.se
    > SkypeID: marston.johnston
    > Phone: +46-31-7864901
    > Only the fruitful thing is true!
    > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    > 
    > 
    > On 2017-09-14, 14:57, "Damjan Jelić" <damjan.jelic at fmf.uni-lj.si> 
    > wrote:
    > 
    >     Hi,
    >     i did try numerous variations.. :(
    >     that function is not working for me and i was hoping for 
    > dim_pqsort_n
    >     which can permute any dimension but it permutes everything (all 
    > columns)
    >     and i got lost in all of that.
    > 
    > 
    >     
    > https://www.ncl.ucar.edu/Document/Functions/Built-in/dim_pqsort.shtml
    >     > I think it can do what you want. Give it a try with your test 
    > example.
    >     > The examples are pretty good.
    >     >
    >     > /M
    >     >
    >     > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    >     > Marston S. Ward, PhD
    >     > Department of Earth Sciences
    >     > University of Gothenburg, Sweden
    >     > Email: marston.johnston at gu.se
    >     > SkypeID: marston.johnston
    >     > Phone: +46-31-7864901
    >     > Only the fruitful thing is true!
    >     > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    >     >
    >     >
    >     > On 2017-09-14, 14:20, "ncl-talk on behalf of Damjan Jelić"
    >     > <ncl-talk-bounces at ucar.edu on behalf of 
    > damjan.jelic at fmf.uni-lj.si>
    >     > wrote:
    >     >
    >     >     Dear NCL support,
    >     >
    >     >     i have perhaps a bit silly question but i stuck up and have 
    > to ask:
    >     >
    >     >     suppose i have 2D array like:
    >     >        2015     1     1
    >     >        2016     2     1
    >     >        1981     1     2
    >     >        1982     1     0
    >     >        1981     0     2
    >     >     how can i sort it out in a way that first column is from 
    > 1981-2016
    >     > but
    >     >     rows stay attached to the year so on the end it looks like 
    > this:
    >     >
    >     >        1981     1     2
    >     >        1981     0     2
    >     >        1982     1     0
    >     >        2015     1     1
    >     >        2016     2     1
    >     >
    >     >     the order within same year (1981) is not relevant.
    >     >     Is there some NCL function for that and how to use it 
    > correctly?
    >     >
    >     >     Kindly,
    >     >     Damjan
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