Ferret Version 5.6 Release Notes

The new /RANGE qualifier lets us use REPEAT looping which is independent of any grid or axis. You may define a range to loop over, and optionally name the repeat counter. The name that is used is undefined after the loop terminates. This syntax can be used for nested loops, and can be used together with standard REPEAT loops which use I=,J=,X=, and so on.

A word of caution is in order about REPEAT/RANGE. If you find yourself doing some operation to every element of a variable along an axis, or using REPEAT to do regridding, integrals or averages, you will want to rethink whether you are unnecessarily complicating your scripts and probably slowing your calculations. Do not use REPEAT to duplicate Ferret's capability of operating on entire grids or axes in a single command. Using Ferret's commands for regridding, transformations, and so on will be more efficient and foolproof than "programming" with REPEAT loops. New Ferret users should study Chapter 1-4 of the Ferret Users Guide for guidance on using Ferret expressions for computation.

Examples of REPEAT/RANGE=[/NAME=]:

• Simplest case

      yes? LET a = 12
      yes? REPEAT/RANGE=1:3 (LET a = `a+2`; LIST a)
        !-> REPEAT: REPCOUNT:1
         !-> DEFINE VARIABLE a = 14
                     VARIABLE : 14
                  14.00
        !-> REPEAT: REPCOUNT:2
         !-> DEFINE VARIABLE a = 16
                     VARIABLE : 16
                  16.00
        !-> REPEAT: REPCOUNT:3
         !-> DEFINE VARIABLE a = 18
                     VARIABLE : 18
                  18.00
   

• With a named loop counter

      yes? REPEAT/RANGE=1:7:3/NAME=s (LIST/NOHEAD s)
        !-> REPEAT: S:1
                  1.000
        !-> REPEAT: S:4
                  4.000
        !-> REPEAT: S:7
                  7.000
   

• To loop over a list (FOREACH functionality) where the loop is independent of any region that may be set

      yes? SET REGION/x=300:360/y=40:60/z=0:100/t="1-jan-2000:1-jan-2004"
  
      yes? LET file_list = {"month_2.nc", "month_5.nc", "month_8.nc"}
  
      yes? REPEAT/RANGE=1:3/NAME=m (LET name = file_list[i=`m`]; \
                                    USE `name`; \
                                    GO myscript}
      

• Another example, using the loop counter variable within the loop

      yes? USE levitus_climatology 
      yes? SET REGION/X=100:300/Y=0/Z=10
      yes? PLOT temp
   
      yes? LET r1 = INT( temp[X=@MIN]) + 1
      yes? LET r2 = INT( temp[X=@MAX]) - 1
  
      yes? REP/RANGE=`r1`:`r2`:3/NAME=tt (PLOT/OVER MAX(temp,`tt`) )
  
       !-> REP/RANGE=23:29:3/NAME=tt (PLOT/OVER MAX(temp,`tt`) )
      !-> REPEAT: TT:23
       !-> PLOT/OVER MAX(temp,23)
      !-> REPEAT: TT:26
       !-> PLOT/OVER MAX(temp,26)
      !-> REPEAT: TT:29
       !-> PLOT/OVER MAX(temp,29)
   
   

Qualifiers /GRATICULE, /HGRATICULE and /VGRATICULE
set graticule lines across plots at the tic marks. They are available on the PLOT, CONTOUR, FILL, SHADE, and VECTOR commands.

PLOT/GRATICULE[=linetype]
is a single command to turn the graticules for both the horizontal and the vertical axes on. By default the graticules are drawn as thin black lines at each large tic mark. The colors and the thickness settings have the same options as the settings for PLOT lines. The syntax is

    yes? PLOT/GRAT=(dash,COLOR=red) var

    yes? SHADE/GRAT=(COLOR=white) rose

    yes? PLOT/GRAT=(THICK=3)/t=1-jan-1990:1-jan-2002 my_data

PLOT/HGRATICULE[=linetype] /VGRATICULE[=linetype]
These two qualifiers give the user separate control of horizontal and vertical tics. Each takes the same optional arguments as /GRATICULE.

New palette files