[ferret_users] Aspect, bad values using poly_vector.jnl

[Serena Illig <serena.illig.ird@xxxxxxxxx>]

Dear Ferret users,

I hope this email finds you well.

I am writing regarding some vector plots. I am using PyFerret v7.63 on Linux Ubuntu (via miniconda) but I have the same issues with PyFerret v7.62 and ferret v6.71.

I am drawing an hovmuller vector plot (x-t plot) of the wind stress anomalies along the equator for 2021, overlaying SST anomalies.
I am pretty happy with the result of the command VECTOR/OV without specifying /ASPECT, because the time axis does not have a spatial scale. However, I prefer the look of the arrows drawn by the "go poly_vector.jnl" script, associated with POLYGON/OVER.

I encountered 2 problems using the poly_vector.jnl script:

1) Using go poly_vector.jnl, my first problem was the difference in the axis scaling (y_scale/x_scale) between the VECTOR/OV plot and the poly_vector.jnl script.
---> I thus modified the poly_vector scrip.jnl (see script attached) to include the possibility to adjust the direction of the vectors just like with /ASPECT in the VECTOR/OV plot.
I created a 7th input argument, that corrects the direction of the arrows.
The script works with or without specifying the 7th argument and mimics the arrows drawn with the command VECTOR/OV (I do not know why I had to scale with sqrt(2), see below).

let vect_aspect = $7"-1."

! Compute the vector direction on the plot
let vect_rotation= if vect_aspect lt 0 then plt_y_per_inch/plt_x_per_inch else vect_aspect*(plt_x_inch_span/plt_y_inch_span)*(2)^0.5
let pi = 4*atan(1)
let vect_dir = atan2(vect_rotation*vect_y_comp/plt_y_per_inch, vect_x_comp/plt_x_per_inch)

2) My second problem was linked to bad values. I do not want to plot vectors if the arrows are too small. I thus masked the wind stress components using a simple if loop.
It works fine until I add a value to color the arrows.
*** POLYGON/OVER/NOLABEL/KEY/NOAXES/LINE PLT_X_ARROW, PLT_Y_ARROW, MY_VALUES[J=1:132] ***
I chose that the color is associated with the x-component of the wind stress anomalies that have large positive values in June 2021. I get a shift of the colors as if the bad values of MY_VALUES are used for the next arrow being transparent (see the tiny arrow in March at 2.5°E in My_plot_shifted.png). I get the same behavior if I do not mask MY_VALUES, except that the color is white (according to my color scale).
To solve my problem I created an external function (keep_good.F) that removes the bad values by shifting the valid data (see function attached and My_plot_corrected.png).

Maybe this issue has already been reported?

Have a nice day,

Serena Illig

.¸. , . .·´¯`·
 ><(((º>     `·.¸.·´¯`·...¸><(((º>¸.¸. , . .·´¯`· ><(((º> .
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Attachment: poly_vectors2.jnl
Description: Binary data

Attachment: My_plot_shifted.png
Description: PNG image

Attachment: My_plot_corrected.png
Description: PNG image

* 
*  keep_good.F in 6D
* 
*  Serena Illig
*  June 2022
* 
*  Remove the bad values by shifting the data !!!
* 

      SUBROUTINE keep_good_init(id)

      INCLUDE 'EF_Util.cmn'

      INTEGER id, arg
*
* **********************************************************************
*                                            USER CONFIGURABLE PORTION |
*                                                                      |
*
      CALL ef_set_desc(id,'Keep good data and remove bad values')
*
      CALL ef_set_num_args(id, 1)
      CALL ef_set_has_vari_args(id, NO)
      CALL ef_set_axis_inheritance_6d(id, NORMAL, 
     .     IMPLIED_BY_ARGS, IMPLIED_BY_ARGS, IMPLIED_BY_ARGS,
     .     IMPLIED_BY_ARGS, IMPLIED_BY_ARGS)
      CALL ef_set_piecemeal_ok_6d(id, YES, YES, YES, YES, YES, YES)
*
      arg = 1
      CALL ef_set_arg_name(id, arg, 'A')
      CALL ef_set_arg_desc(id, arg, 'Field to be Processed')
      CALL ef_set_axis_influence_6d(id, arg, YES, YES, YES, YES, YES, YES)
*
*                                                                      ^
*                                                                      |
*                                            USER CONFIGURABLE PORTION |
* **********************************************************************

      RETURN 
      END


* 
*  In this subroutine we compute the result
* 
      SUBROUTINE keep_good_compute(id, arg_1, result)

      IMPLICIT none

      INCLUDE 'EF_Util.cmn'
      INCLUDE 'EF_mem_subsc.cmn'

      INTEGER id, arg

      REAL bad_flag(EF_MAX_ARGS), bad_flag_result
      REAL arg_1(mem1lox:mem1hix, mem1loy:mem1hiy, mem1loz:mem1hiz,
     .           mem1lot:mem1hit, mem1loe:mem1hie, mem1lof:mem1hif)

      REAL result(memreslox:memreshix, memresloy:memreshiy,
     .            memresloz:memreshiz, memreslot:memreshit,
     .            memresloe:memreshie, memreslof:memreshif)
*
* After initialization, the 'res_' arrays contain indexing information 
* for the result axes.  The 'arg_' arrays will contain the indexing 
* information for each variable's axes. 
*
      INTEGER res_lo_ss(6), res_hi_ss(6), res_incr(6)
      INTEGER arg_lo_ss(6,EF_MAX_ARGS), arg_hi_ss(6,EF_MAX_ARGS),
     .     arg_incr(6,EF_MAX_ARGS)
*
* **********************************************************************
*                                            USER CONFIGURABLE PORTION |
*                                                                      |
*                                                                      V
      INTEGER i,j,k,l,m,n
      INTEGER i1,j1,k1,l1,m1,n1   
*
      CALL ef_get_res_subscripts_6d(id, res_lo_ss, res_hi_ss, res_incr)
      CALL ef_get_arg_subscripts_6d(id, arg_lo_ss, arg_hi_ss, arg_incr)
      CALL ef_get_bad_flags(id, bad_flag, bad_flag_result)
*
      DO 105 n=res_lo_ss(F_AXIS), res_hi_ss(F_AXIS)
      DO 104 m=res_lo_ss(E_AXIS), res_hi_ss(E_AXIS) 
      DO 103 l=res_lo_ss(T_AXIS), res_hi_ss(T_AXIS)
      DO 102 k=res_lo_ss(Z_AXIS), res_hi_ss(Z_AXIS)       
      DO 101 j=res_lo_ss(Y_AXIS), res_hi_ss(Y_AXIS)
      DO 100 i=res_lo_ss(X_AXIS), res_hi_ss(X_AXIS) 
         result(i,j,k,l,m,n)=bad_flag_result
 100  ENDDO
 101  ENDDO
 102  ENDDO
 103  ENDDO
 104  ENDDO
 105  ENDDO

      DO 205 n1=arg_lo_ss(F_AXIS,ARG1), arg_hi_ss(F_AXIS,ARG1)
      DO 204 m1=arg_lo_ss(E_AXIS,ARG1), arg_hi_ss(E_AXIS,ARG1)  
      i=res_lo_ss(X_AXIS)
      j=res_lo_ss(Y_AXIS)
      k=res_lo_ss(Z_AXIS)
      l=res_lo_ss(T_AXIS)     
      DO 203 l1=arg_lo_ss(T_AXIS,ARG1), arg_hi_ss(T_AXIS,ARG1)
      DO 202 k1=arg_lo_ss(Z_AXIS,ARG1), arg_hi_ss(Z_AXIS,ARG1)       
      DO 201 j1=arg_lo_ss(Y_AXIS,ARG1), arg_hi_ss(Y_AXIS,ARG1)
      DO 200 i1=arg_lo_ss(X_AXIS,ARG1), arg_hi_ss(X_AXIS,ARG1) 
         if (arg_1(i1,j1,k1,l1,m1,n1).ne.bad_flag(1)) then
            result(i,j,k,l,m1,n1)=arg_1(i1,j1,k1,l1,m1,n1)
            if (i.ne.res_hi_ss(X_AXIS)) then
               i=i+1
            else
               i=res_lo_ss(X_AXIS)
               if (j.ne.res_hi_ss(Y_AXIS)) then
                  j=j+1
               else
                  j=res_lo_ss(Y_AXIS)
                  if (k.ne.res_hi_ss(Z_AXIS)) then
                     k=k+1
                  else
                     k=res_lo_ss(Z_AXIS)
                     l=l+1
                  endif                               
               endif          
            endif
         endif
*            
 200  ENDDO
 201  ENDDO
 202  ENDDO
 203  ENDDO
 204  ENDDO
 205  ENDDO
*                                                                      ^
*                                                                      |
*                                            USER CONFIGURABLE PORTION |
* **********************************************************************

      RETURN 
      END