Re: [ferret_users] extracting info from axes

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi Ge Peng,
Billy's suggestions will all work well. I have some more ideas to add as 
well.  The RETURN= keyword will also give you access to information 
about the variable and grid.

If var is a variable in your dataset, then you can use `var,return= `  
will give you the axis ends in the current context you have set with a 
"set region", and also the units of the variable or the axes.  For example,

yes? set region/i=33/j=12/k=5/l=23
yes? define symbol label_ijkl = \
 `var,return=xstart`, `var,return=ystart`, depth(`var,return=zunits`):, 
`var,return=zstart`, `var,return=tstart`

yes? show symbol label_ijkl

You can control the precision of the output by adding a precision 
specifier, for example, `var,RETURN=tstart,precision=3` and you can turn 
the labeling of the longitude and latitude outputs on or off by setting 
or canceling the modes LONG_LABEL and LATIT_LABEL.

The functions TAX*  also give you ways to return a date string,

yes? show function TAX*

Ansley


William.S.Kessler wrote:
> Hi Ge Peng -
>
> Any quantity that is written on a default plot is available as a symbol.
>
> For example, if you:
>
> plot/i=242/j=14/k=22/l=8 varname
>
> The plot and title will contain the information you want (perhaps in 
> the upper left corner, or in the title below the plot).
>
> AFTER making such a plot, these symbols will be found by:
>
> yes? ppl listsym
>
> These symbols will generally be numbered lab4, lab5, lab6, .... 
> (lab1,2,3 are the standard Ferret info that appears in the upper right 
> corner of the plot).
>
> You can write these in subsequent plots as follows:
>
> label xpos ypos center angle size ($lab4)
>
> And, you can get fancier by noticing that these label numbers are 
> flagged by other symbols in the list. You don't have to do that long 
> listing every time. For example, the label for the plot longitude (if 
> it is relevant) is flagged by the symbol labnum_x. So, you can always 
> write the longitude by:
>
> label xpos ypos center angle size ($lab($labnum_x))
>
> In addition to the location identifiers, there are also the labels for 
> the dataset (flagged by labnum_dset) and others as appropriate.
>
> The one rule to remember is that these symbols are defined ONLY AS THE 
> PLOT IS DRAWN. You MUST make a standard plot (without /NOLABEL) to 
> define them before you can use them.
>
> Billy K
>
>
> On 18/02/2009, at 4:19 PM, Ge Peng wrote:
>
> > Hi Ferret Users,
> >
> > Apology if this request is too elementary.
> >
> > I would like to extract grid info from a data set for the purpose of
> > labeling. For example, for a given region/i=242/j=14/k=22/l=8, I have 
> > the
> > lon, lat, z, and time as follows:
> >
> > yes? list x[gx=xt_ocean]
> >              VARIABLE : X
> >                         axis XT_OCEAN
> >              LONGITUDE: 38.5W(-38.5)
> >          -38.50
> > yes? list y[gy=yt_ocean]
> >              VARIABLE : Y
> >                         axis YT_OCEAN
> >              LATITUDE : 68.5S
> >          -68.50
> > yes?  list z[gz=zt_ocean]
> >              VARIABLE : Z
> >                         axis ZT_OCEAN
> >              DEPTH (m): 215
> >           215.0
> >
> > yes? list t[gt=TIME]
> >              VARIABLE : T
> >                         axis TIME
> >              TIME     : 07-FEB-1999 12:00 JULIAN
> >           2228.
> >
> > I would like to define a label, which should be something like
> > "38.5W, 68.5S, DEPTH (m): 215, 07-FEB-1999"
> >
> > Of cause, it will be different for a different region if I change i,j,k,
> > or l values.
> >
> > Is it a way to create the label dynamically?
> >
> > Thanks,
> >
> > --- Peng