Ferret Version 5.5 Release Notes

New Features and Enhancements in version 5.5

• Subspan modulo axes allow time and longitude axes which are less than the modulo repeat length to be treated as modulo axes.
• New NetCDF attributes describe the axis direction.
• New Ferret command-line switch: > ferret -nojnl starts Ferret without a journal file.
• New MODE LOGO and MODE LABEL allows turning on and off the Ferret logo and labels.
• Fprint (gksm2ps) has a switch to produce CMYK postscript output.
• A set of symbols lets us reuse automatic levels previously set for CONTOUR, FILL, and SHADE plots.
• Hard program limits increased.
• GKS cellarray call implemented for x-windows only, for shade plots of data with regular grids.
• GKS dot, used for PLOT/SYMBOL=DOT restored.

• Can now regrid to a user-defined variable that has not been loaded.
• String variables in 4 dimensions can be handled in a NetCDF file.
• LIST/CLOBBER failed when file exists under linux.
• LIST/APPEND clobbered the file, on SGI machine.
• 24-bit color and GIF creation problems on Solaris consoles.
• String variable/SET GRID bug caused Ferret crash.
• Fixed let a= spawn bug; crashed under Linux "yes? let a = {spawn:"cat input.txt"}
• Date-reading bug with FILE/FORM=DELIMITED fixed.
• POLYGON/OVER had time-axis error with non-standard calendars; fixed.

New Features and Enhancements

• Ferret V5.5 introduces the concept of a "sub-span modulo axis" -- an axis where the range is a sub-range of a full modulo cycle. As of V5.5, longitude axes of length up to 360 degrees and climatological time axes will always be detected as modulo, or as sub-span modulo when appropriate, unless Ferret is specifically directed that the axis is NOT modulo, e.g. by a CANCEL AXIS/MODULO command.

  The modulo length of an axis defined on the Ferret command line is set with an argument to the MODULO qualifier. Here is an example showing an axis defined explicitly as a modulo axis, and another which is modulo by default.

        yes? DEFINE AXIS/MODULO=100/x=41:55:1 xax_subspan
        yes? DEFINE AXIS/X=100:300:10/UNITS=degrees_longitude xax_lonspan
  

  The output of SHOW AXIS reflects this:

        yes? show axis xax*
         name       axis              # pts   start                end
         XAX_SUBSPAN                    6mr   41                   46
           Axis span (to cell edges) = 6 (modulo length = 100)
         XAX_LONSPAN LONGITUDE         21mr   100E                 60W
           Axis span (to cell edges) = 210 (modulo length = 360)

  In the NetCDF files you will now sometimes see the modulo attribute taking a value. Continuing the example above,

        yes? LET v1 = X[GX=xax_subspan] +10
        yes? let v2 = SIN(X[GX=xax_lonspan])
        yes? SAVE/FILE=test_subspan_modulo.nc v1, v2
        yes? SPAWN ncdump test_subspan_modulo.nc
        ...
        variables:
        	double XAX_SUBSPAN(XAX_SUBSPAN) ;
        		XAX_SUBSPAN:modulo = 100. ;
        ...
          double XAX_LONSPAN(XAX_LONSPAN) ;
  		    XAX_LONSPAN:modulo = 360. ;
  

  The importance of the sub-span modulo axes is to take the first of two steps that will make it possible for users largely to ignore differences in encodings of longitude and climatological time -- e.g. the blending of data in plots and analyses where the data come from data sets that are encoded variously as -180:180, 0:360, etc. Thus, for example, in V5.5 you can refer to my_subspan_var[g=another_var] and get a meaningful answer as long as the grids occupy the same region on the globe, regardless of longitude encoding. (The second step, for a future release, will address the longitude encoding of scattered data.)

  There is an implied void point in a sub-span modulo axis that fills the gap between the end of the axis and the start of the next modulo cycle. The data value at this point will always be the missing value flag (except for pseudo-variables such as "X[g=my_subspan_axis]"). Transformations such as smoothers do not operate across the void point.




• New NetCDF attributes are available to describe the axis direction.
  • AXIS attribute for coordinate variables, specifies the coordinate direction of the axis, e.g. my_var:AXIS = "Z"
  
  Files written by Ferret now include the AXIS= attribute on coordinate variables.
  • CARTESIAN_AXIS attribute may also be used to specify the direction of an axis, e.g. my_var:CARTESIAN_AXIS="T"
  • The attribute "positive=" is handled in a more general way. It may apply to any axis, with positive="up" or positive="down". Note that Ferret does not recognize positive="down" except for depth (z) axes, and will ignore this if it is specified for other axes.
  • Order of precedence is improved for making use of attributes when determining the direction of an axis in a NetCDF file. The order is: AXIS, CARTESIAN_AXIS UNITS, POSITIVE=, and then the axis name.


• New Ferret command-line switch: ferret -nojnl starts Ferret without a journal file. Within the Ferret session, SET MODE JOURNAL may be used to turn on journaling and set the journal file name if desired.



• New MODE LOGO and MODE LABEL allows turning on and off the Ferret logo and labels.



   yes? CANCEL MODE logo   ! turns off the 3-line Ferret logo for subsequent plots
   yes? CANCEL MODE labels ! implements PLOT/NOLABEL for subsequent plots.



• Fprint (gksm2ps) has a new switch, -C, to produce CMYK postscript output. For example:
  

    > Fprint -C -o my_file.ps metafile.plt

  Note that you will also want to choose a palette that is designed for CMYK output. See the FAQ "How can I get CMYK format for postscript files? " for a list of CMYK-friendly palettes, and for a description of the steps needed to create your own CMYK palettes.



• New symbols are defined to save the state of automatic levels. When a CONTOUR, FILL, or SHADE command is issued, the following are set, as applicable: LEV_MIN, LEV_MAX, LEV_NUM, LEV_DEL, and LEV_TXT. LEV_TXT contains the user input to the LEV qualifier. For example:

   yes? USE coads_climatology
   yes? CONTOUR/L=1/LEV=30 sst
   yes? SHOW SYM LEV*
   LEV_TEXT = "30"
   LEV_MIN = "-2"
   LEV_MAX = "32"
   LEV_NUM = "35"
   LEV_DEL = "1"

   yes? SHADE/L=5/LEV=(($LEV_MIN), ($LEV_MAX), 2) sst
   yes? SHOW SYM LEV*
   LEV_TEXT = "(-2, 32, 2)"
   LEV_MIN = "-2"
   LEV_MAX = "32"
   LEV_NUM = "18"
   LEV_DEL = "2"

• Hard program limits are increased:
• 100 open datasets, was 30
  Note: due to DODS and NetCDF library constraints, this is in fact limited to 32
• 2000 user variables, was 500
• 2000 dataset variables, was 500
• 1500 dynamic axes, was 500
• 250 levels allowed in palette files, was 100
• 100 number of user-defined regions, was 10
• 24 characters, for length of region names, was 4
• 512 characters, length of filenames in descriptor files, was 128
• 1000 files may be listed in a descriptor file, was 500


• GKS cellarray call implemented for x-windows only, for shade plots of data with regular grids.



• GKS dot, used for PLOT/SYMBOL=DOT restored.