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Re: various misc. items

> Donald S. Dunbar wrote:
> I often use Ferret to plot data over small regions where the distance
> scale is constant.  I invariably want to add a nice looking distance
> scale, and do so during post-processing of a GIF image.  Is there a
> more direct way?  Has someone written a script that will do this on a
> Ferret plot?

Hi Donald,

Have a look at the "%XAXIS" and %YAXIS" commands (in thre PLOT+ Users
Guide in your $FER_DIR/docs directory). These should allow you to do
what you are after.

> When I plot lon/lat axes for these small areas the axis tick labels
> are in decimal degrees.  It would be nice to have an option for deg,
> min, sec labels where the degree and or minute value appears only as
> many times as required (e.g., if the range were from 124.15 to 124.25
> then the degree label would appear only once).  At present I (again)
> do this during post-processing of a GIF image.

Unfortunately, this style of formatting is not available.
> When I input west longitudes from a file in the format "xx.xxW" and
> plot the data, the X-axis is inverted.  For example, if the range is
> 135W to 133W then the axis is plotted from 133 to 135.  My solution is
> to input the angles as negative values; however, this results in
> negative tick labels.  Am I doing something wrong or is this a bug?

Without more detail on the way in which the plot is constructed, I can
suggest only some general approaches.

The PLOT+ graphics are a bit fussy about the encoding of longitudes. In
the PLOT+ Users guide you'll find "LONW" and "LONE" formatting options
to handle east and west encoding.

Alternatively, you can define a variable:
	LET lon360 = my_longitude + 360
and then base your plots on the variable "lon360".

> On the subject of aspect ratios in windows.  It seems to me that if
> the X and Y scales are equal, then there should be a way of having
> Ferret generate the correct aspect ratio automatically after
> specifying either the X or Y dimension.  At present I am required to
> determine (min,max) ranges for both X and Y axes, do a little bit of
> arithmetic, then specify the ASPECT=Y/X option.  This strikes me as
> something that arises so frequently that a new option is warranted,
> thus letting Ferret do the math automatically.

Actually, there is a very general approach to this kind of calculation
-- Ferret "immediate mode expressions". You can embed the simple
arithmetic of the aspect ratio calculations into the SET WINDOW/ASPECT
command directly. Example:

 LET my_aspect = (my_y[Y=@max]-my_y[Y=@min])/(my_x[X=@max]-my_x[x=@min])

Note the grave accents to immediately execute the arithmetic and the
":AX" to specify it is the ratio of axis lengths that is being
> I sometimes want to have more than one color bar appear on a plot.  Is
> this possible?  When I overlay one shading on top of another I would
> expect both color keys to appear, however this does not
> happen—only the original key appears.  Is there a way of having
> more than one color key? 

This can be achieved only by using multiple viewports. You can define
two identical viewports (layers on top of one another) and have complete
independence of the graphic contents of each layer. The PPL SHASET
command (again, the PLOT+ Users Guide -- Enhanced Features Supplement)
allows you to control the placement of multiple keys.

> Also, can one control the labeling (e.g.,
> size, frequency, side of scale) and position (e.g., left or right side
> of plot) of the key?

There are commands to control for all of these features. See Chapter 6:
CUSTOMIZING PLOTS (esp. section 3.2) in the Ferret Users Guide (on the
Web at

Good questions. I hope these answers help.

	- steve
>   Donald S Dunbar <dsd@oar.com>
>   President/Physical Oceanographer
>   Ocean Applied Research Ltd
>   Donald S Dunbar
>   President/Physical Oceanographer  <dsd@oar.com>
>   Ocean Applied Research Ltd
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Steve Hankin
NOAA/PMEL, 7600 Sand Point Way NE, Seattle, WA 98115-0070
ph. (206) 526-6080 -- FAX (206) 526-6744

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