[ncl-talk] Function return

Prashanth Bhalachandran prashanth.bhalachandran at gmail.com
Sat Oct 14 08:26:17 MDT 2017


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,var01,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 <mailto: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 <mailto:marston.johnston at gu.se>
> SkypeID: marston.johnston 
> Phone: +46-31-7864901 
> Only the fruitful thing is true!
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  
>  
> From: ncl-talk <ncl-talk-bounces at ucar.edu <mailto:ncl-talk-bounces at ucar.edu>> on behalf of Prashanth Bhalachandran <prashanth.bhalachandran at gmail.com <mailto:prashanth.bhalachandran at gmail.com>>
> Date: Saturday, 14 October 2017 at 03:57
> To: <ncl-talk at ucar.edu <mailto: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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