Release Notes for Ferret version 4.0

At the time of this writing (29 Mar) the GUI is not available on all of the Unix platforms supported by Ferret. (Watch for announcements in the Ferret users group). We are enthusiastic about this interface and believe that it will be a pleasure to use and a real value. We need to stress, however, that at this time the GUI is still under development.

If you choose to use the GUI you are implicitly becoming a BETA tester. We make two requests of you:

Version 4.0 includes "immediate mode" mathematical expressions -- that is, numerical expressions that may be embedded anywhere within a command line, to be evaluated immediately by Ferret - before the command, itself, is parsed and executed. Immediate mode expressions are enclosed in grave acccents, the same syntax used by the Unix C shell. Prior to parsing and executing the command Ferret will replace the full grave accent expression, including the accent marks, with an ASCII string representing the numerical value. For example, if the given command is

		CONTOUR/Z=`temp[X=180,Y=0,Z=@LOC:15]` salt

		CONTOUR/Z=234.5 salt

• the expression must evaluate to a single number, a scalar
• the numerical value generated will have 5 significant digits
• if the result is invalid the numerical string will be "bad"
• the region qualifiers attached to the command **will** be used in the evaluation of the grave-accented expressions
• if multiple grave-accented expressions are used in a single command they will be evaluated from left to right within the command. This means that grave-accented expressions used to specify region information (e.g. the above example) may influence the evaluation of other grave-accented expressions to the right
• when grave-accented expressions are used within commands which are arguments of a REPEAT command their evaluation is deferred until the commands are actually executed. Thus the grave-accented expressions are re-evaluated at each loop index of the REPEAT command
• grave accents have a higher priority than any other syntax character. Thus grave accent expressions will be evaluated even if they are enclosed within quotation marks, parentheses, square brackets, etc.
• substitutions based on dollar-signs (command script arguments) will be made before grave accent expressions are evaluated
• a double grave accent will be translated to a single grave accent and not actually evaluated. Thus double grave accents provide a mechanism to defer evaluation so that grave accent expressions may be passed to the Unix command line with the SPAWN command or may be bassed as arguments to GO scripts (to be evaluated INSIDE the script.
• the state of mode verify will determine if the evaluation of the grave accent expression is echoed at the command line -- similar to REPEAT loops

o The limit to the number of variables that may be simultaneously read from an ASCII or binary file (the "/VARIABLES=" qualifier on the FILE command) has been increased from 10 to 20.

... memory size can be specified at the Unix command line (above) or it can be reconfigured while FERRET is running with these commands:

SHOW MEMORY

shows current memory size

SET MEMORY/SIZE=xxx (in MegaWords)

dynamic memory reconfigure

	e.g. yes? SET MEMORY/SIZE=4

The command SET MODE VERIFY:ALWAYS will place Ferret in a state where MODE VERIFY cannot be cancelled by commands in a GO script. This means that all lines executed within the GO script will be echoed at the console -- a feature that can assist with debugging GO scripts.

	FRAME/FORMAT=GIF/file=gif_file_name.gif

New qualifiers have been added to the SAVE (alias LIST/FORMAT=CDF) command to specify the range of the intended output file independent of the range of data to be inserted into the file. The new qualifiers are /ILIMITS, /JLIMITS, /KLIMITS, /LLIMITS, /XLIMITS, /YLIMITS, /ZLIMITS, /TLIMITS.

An example usage: Suppose the data set "giant3D" contains the variables u and v each on a grid that is nX x nY x nz = 1000 x 1000 x 200 = 200 Meg in size. Suppose that we wish to create an output file of "speed = (u^2+v^2)^0.5". We cannot fit the entire calculation into memory but we can compute one vertical level at a time. Here we use "/KLIMITS" to create an output file with all of the vertical levels. Then we use "/APPEND" to insert the levels into the file.

	
   yes? SET DATA giant3D  ! nX x nY x Nz = 1000 x 1000 x 200 = 200 Meg
   yes? LET speed = (u^2+v^2)^0.5
   yes? SAVE/KLIMITS=1:200/FILE=giant_speed.cdf   speed[K=1]
   yes? REPEAT/K=2:200 SAVE/APPEND/FILE=giant_speed.cdf  speed

The qualifier /HEADING now can take the argument "enhanced" to produce ASCII output that is self-documenting and machine readable. This is used in the "ASCII file" output on the FERRET/WWW server. The /HEADING=enhanced feature requires that the /FORMAT qualifier be used to specify the output format. If /FORMAT is given but no FORTRAN format is actually specified then the data will be listed using (5(1PG12.5)) but documented as using the compatible but simpler format (5F12.5)

	yes? LIST/FORMAT/HEADING=ENHANCED my_variable

The title of a netCDF data set may be set explicitly using

    SAVE/TITLE="My choice of data set titles"  whatever_variables,...

By default netCDF file outputs will **not** contain attributes that locate the output fields within a larger coordinate framework (the attributes parent_grid, slab_min_index, ...). To obtain this type of netCDF output file use the SAVE command with the qualifier /HEADING=enhanced

The command GO/HELP journal_file brings up the Unix "more" command to view the documentation at the heading of a journal file.

The function DAYS1900(year,month,day) provides the number of days from 1-JAN-1900 (sensitive to leap years). This function is helpful in processing many types of ASCII tabulated data.

Modulo axes are now fully supported in netCDF, ASCII, and binary files. FERRET is now capable of simultaneously providing "modulo" data on one to 4 axes. (For example, a monthly climatological set from X=0 to 360 may be requested with "/L=1:24/X=180:540", which requires simultaneous modulo operations on both X and T).

Support has been added for netCDF coordinate axes that are decreasing-ordered in the netCDF file. The fact that the axes are reversed will be transparent to the user. Output netCDF files will always be increasing-ordered.

The "*" character may now appear on the right hand side of a substitution. It represents the entire argument string passed to the script. Thus, for example

	$1% |*>="*"%

The command LIST/FORMAT=STREAM allows Ferret to write binary output files with no record information embedded. These files are easily readable by C programs or can be read by FORTRAN programs that use OPEN(ACCESS='DIRECT",RECL=len,...) and READ (UNIT=lun,REC=irec).

The binary output files from FERRET that are produced with LIST/FORMAT=unformatted are suitable as input to FORTRAN programs which omit "ACCESS='DIRECT'" (or use "ACCESS='SEQUENTIAL'") and use sequential reads (omitting "REC=irec").

Greatly improved performance of regridding operations (VARIABLE[G=new_grid]) that involve differing time axes on source and destination grids.

polar_2d.jnl, polar_grid.jnl

handle South pole, too

GO land

has nations and states GO fland

provides "transparent" (see-through) masks as well as "detailed" masks

GO basemap

provides a varietty of basemap stypes

dark_land_sea.spk

like land_sea.jnl but subtler land colors

white_centered.spk

useful to highligh areas of significant anomaly

low_blue.spk, low_red.spk, low_green.spk

similar to their "no_***.spk" relatives but avoid such dark colors at the ends of the spectrums. This makes them work better with dark overlays like land masks.

By default PLOT/VS will now plot symbols rather than a line. Use the /LINE qualifier to reproduce previous behavior.

The speed of frame grabbing with the FRAME command or /FRAME qualifier has been greatly increased.

Ferret now supports files that are encoded on longitudes -180 to 180. (Previously, it had been recommended to use only positive longitudes.) However, negative longitudes should be used with care. If a file is encoded using all positive longitudes on a modulo axis and a plot which begins at a negative longitude is requested there is a risk of crashing Ferret because negative (left hand) modulo translations are not supported. The GO scripts land and fland have not yet been updated to support negative longitudes.

When graphical output is created from within a GO script Ferret will define the PLOT+ symbol 'GO_FILE'. This can be used with commands like

	LABEL xpos,ypos,center,rotate,size 'GO_FILE'

Note: In version 4.01 and higher a preferred syntax that uses Ferret symbols is:

	LABEL xpos,ypos,center,rotate,size ($GO_FILE)