[ncl-talk] Function return

Alan Brammer abrammer at albany.edu
Sat Oct 14 13:44:04 MDT 2017


> I don’t know what my dimensions of wnout will be. Will it be a 251x251x73
 array?

It will
​ be a list, there won't be array dimensions.  You do not need to define
wnout before hand.
likewise, you do not need to define ​var0 or var1 before hand.

e.g.


 a = addfile(filename,"r")
 u10 = a->u10
 v10 = a->v10
 slp = a->slp

;;;;;;;;;;;;;;;;; Constants ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

 R         = 6371
 d2r       = atan(1.0)/45; Equivalent of pi/180 - 0.01745329
 r2d       = 1.0/d2r
 toknots   = 1.94384
 pi        = 3.14159

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; this section wasn't really needed

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

 slpsub    = slp(time,0,:,:) ; X is now a 2D array
 speed     = wind_speed(u10(time,0,:,:),v10(time,0,:,:)) * toknots
 latvals   = u10&lat(0:800)
 lonvals   = u10&lon(0:809)

 coord        = center_find(speed(:,:),slpsub)
 lat1         = coord[0]
 lon1         = coord[1]

;;;;;;;;;;;;;; Find all variables here and store into allvars ;;;;;;;

 wnout        = wn01(latvals,lonvals,lat1,lon1,speed)
 var0         = wnout[0]
 var1         = wnout[1]

printVarSummary(var0)
printVarSummary(var1)

;;;;;;;;;;;;;;;;;;;;;; Write to a netcdf file ;;;;;;;;;;;;;;;;;;

;;;;   I do not think the lines that were here will work.

On Sat, Oct 14, 2017 at 10:26 AM, Prashanth Bhalachandran <
prashanth.bhalachandran at gmail.com> wrote:

> Dear Marston,
> Thank you for your response. I will ensure that the missing values are the
> default ones from NCL. I hope my attaching the code will give you a little
> more context.
>
> My concern is this : If I am returning two arrays var0  and var01 (please
> see the red highlighted portions for array dimensions), how will I receive
> it in the main wrapper script?
>
> That is, if my var0 dimension is : (/251/) and my var01 dimension is
> (/251,73/), and I return the variable from the function using
> return([/var0,var01/]), when I collect it in the wrapper script using
> wnout        = wn01(latvals,lonvals,lat1,lon1,speed),
>
> I don’t know what my dimensions of wnout will be. Will it be a 251x251x73
> array? I do know that I want to extract it as:
>  var0         = wnout[0]
>  var1         = wnout[1]
>
>
> *CODE*
>
>  load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
>  load "/scratch/lustreD/s/sbhalach/DATA/func_center.ncl"
>  load "/scratch/lustreD/s/sbhalach/DATA/func_rtheta.ncl"
>
>  a = addfile(filename,"r")
>  u10 = a->u10
>  v10 = a->v10
>  slp = a->slp
>
> ;;;;;;;;;;;;;;;;; Constants ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
>
>  R         = 6371
>  d2r       = atan(1.0)/45; Equivalent of pi/180 - 0.01745329
>  r2d       = 1.0/d2r
>  toknots   = 1.94384
>  pi        = 3.14159
>
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
>
>  latvals   = new((/801/),float,1e+30)
>  lonvals   = new((/810/),float,1e+30)
>  speed     = new((/801,810/),float,1e+30)
>  var01     = new((/251,73/),float,1e+30)
>  var0      = new((/251/),float,1e+30)
>
>
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
>
>  slpsub       = slp(time,0,:,:) ; X is now a 2D array
>  speed(:,:)   = wind_speed(u10(time,0,:,:),v10(time,0,:,:)) * toknots
>  latvals(:)   = u10&lat(0:800)
>  lonvals(:)   = u10&lon(0:809)
>
>  coord        = center_find(speed(:,:),slpsub)
>  lat1         = coord[0]
>  lon1         = coord[1]
>
> ;;;;;;;;;;;;;; Find all variables here and store into allvars ;;;;;;;
>
>  wnout        = wn01(latvals,lonvals,lat1,lon1,speed)
>  var0         = wnout[0]
>  var1         = wnout[1]
>
> ;;;;;;;;;;;;;;;;;;;;;; Write to a netcdf file ;;;;;;;;;;;;;;;;;;
>
>  system("rm -f $f1_$f2.nc")
>  ncdf = addfile("$f1_$f2.nc","c")
>  ncdf->allvars = allvars
>  ncdf->yymmdd  = $f1
>  ncdf->time    = $f2
>
> -------------------------------------------------------------------
>
> *FUNCTION *
>
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
> load "/scratch/lustreD/s/sbhalach/DATA/func_center.ncl"
>
>
> undef("wn01")
>
>  function wn01(latvals:float,lonvals:float,lat1:float,lon1:float,var:
> float)
>  local R,d2r,r2d,toknots,pi,delr,Xi,Yi,xo,yo,nearxo,nearyo,ovar,var
> 01,var0,c1,b1,orad,otha,arr,a1,a2,a3,a4,a5,a6,a7,a8,a9,r,weights
>
>  begin
>
>  R         = 6371
>  d2r       = atan(1.0)/45; Equivalent of pi/180 or 0.01745329
>  r2d       = 1.0/d2r
>  toknots   = 1.94384
>  pi        = 3.14159
>  delr      = 12
>
>  Xi        = new((/810/),float,1e+30)
>  Yi        = new((/801/),float,1e+30)
>  ovar      = new((/251,73/),float,1e+30)
>  var01     = new((/251,73/),float,1e+30)
>  var0      = new((/251/),float,1e+30)
>  c1        = new((/251/),float,1e+30)
>  b1        = new((/251/),float,1e+30)
>  orad      = ispan(0,1000,delr)
>  otha      = fspan(0,6.283185,73)
>  arr       = new((/3,3/),float,1e+30)
>
>  Xi(:) = R *cos(lat1*d2r)*(lonvals(:)-lon1) * d2r
>  Yi(:) = R *(latvals(:)-lat1) * d2r
>
>  do radius=0,250,1
>   do theta=0,72,1
>
>     xo  = (radius*delr)*cos((theta*5)*d2r)   ; reference points
>     yo  = (radius*delr)*sin((theta*5)*d2r)   ; reference points
>
>     nearxo = ind_nearest_coord (xo, Xi(:), 0)  ;Find the index of the
> bounds
>     nearyo = ind_nearest_coord (yo, Yi(:), 0)
>
>     if(nearxo .eq. 0 .or. nearxo .eq. 809 .or. nearyo .eq. 0 .or. nearyo
> .eq. 800) then
>     ovar(radius,theta) = var(nearyo,nearxo)
>
>   else
>    a1 = var(nearyo+1,nearxo+1)
>    a2 = var(nearyo+1,nearxo)
>    a3 = var(nearyo-1,nearxo-1)
>    a4 = var(nearyo,nearxo+1)
>    a5 = var(nearyo,nearxo)
>    a6 = var(nearyo,nearxo-1)
>    a7 = var(nearyo-1,nearxo+1)
>    a8 = var(nearyo-1,nearxo)
>    a9 = var(nearyo-1,nearxo-1)
>
>    arr = (/ (/a1,a2,a3/), (/a4,a5,a6/), (/a7,a8,a9/)/)   ; Written as nD
> arrays for visual clarity of neighbors
>
>    weights = (/ (/0.0625,0.0625,0.0625/), (/0.0625,0.5,0.0625/),
> (/0.0625,0.0625,0.0625/)/)
>    ovar(radius,theta) =  dim_avg_wgt(ndtooned(arr),ndtooned(weights),1)
>
> ;  Give 50% weight to the nearest location and distribute the other 50%
> equally amongst the neighbours
>    end if
>
>   end do ; Loop over every radius and theta
>  end do    ; End of r-theta loop
>
>   do r=0,250,1
>      var0(r)    =  1/(2*pi)*simpeq(ovar(r,:),5.0*d2r)
>  ; Dimension (/251/)
>      c1(r)      =  1/(2*pi)*simpeq(ovar(r,:)*cos(otha),5.0*d2r)
>      b1(r)      =  1/(2*pi)*simpeq(ovar(r,:)*sin(otha),5.0*d2r)
>      var01(r,:) =  var0(r) + (c1(r)*cos(otha)) + (b1(r)*sin(otha))  ;
> Dimension (/251,73/)
>   end do
>  return([/var0,var01/])
>
>  end
>
>
>
> On Oct 14, 2017, at 12:42 AM, Marston Johnston <shejo284 at gmail.com> wrote:
>
> There is an error in your code:        var0 = new((/251/),float,1e+30
> As a preference, I always find it best to use the default FillValues when
> creating arrays. Read up on missing values/fillvalues on the NCL wedpage.
>
> There is nothing wrong with returning a list from a function, even if the
> dimensions are different. Why would the dimensions matter?
> This doesn’t seem to be your problem. You have not provided enough
> information about your code and variable information (printVarSumary) to
> give a definite answer.
> It seems you need to do some more debugging of your code yourself.
>
> When defining functions, it is good practice to set the define the
> intrinsic variables as “local” as well as using the “undef” function.
> Using the same name for the variables inside and outside the function, if
> you are indeed using a function that is properly designed, can mask a bug
> in your code.
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 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 <+46%2031%20786%2049%2001>
> Only the fruitful thing is true!
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
> *From: *ncl-talk <ncl-talk-bounces at ucar.edu> on behalf of Prashanth
> Bhalachandran <prashanth.bhalachandran at gmail.com>
> *Date: *Saturday, 14 October 2017 at 03:57
> *To: *<ncl-talk at ucar.edu>
> *Subject: *Re: [ncl-talk] Function return
>
> Hello,
> I have a quick question regarding returning of arrays from functions.
>
> In my code, I have two arrays var0 and var01 that I want to return from my
> function. Their dimensionalities are as follows:
>
>
> var0      = new((/251/),float,1e+30
> var01     = new((/251,73/),float,1e+30)
>
>
> At present, I am trying to return this using the command :
>
> return([/var0,var01/]) ; Note that the dimensions of var0 and var1 are
> different.
>
>
> As a result, in my wrapper script, when I receive the variables, it is
> becoming a confusing task.
>
>
>  wnout        = wn01(latvals,lonvals,lat1,lon1,speed)
>  var0         = wnout[0]
>  var1         = wnout[1]
>
>
>  The above return procedure is giving out an error since I don’t know how
> to define the dimensions of wnout. Is there any better way to return two
> arrays of varying dimensions in NCL?
>
>
> Thank you,
> Prashanth
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