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Hi Emile,
The lists of numbers in bx and by do not tell Ferret that they
are longitudes and latitudes.  So Ferret does not know to apply
a "modulo" operation to convert -17 to (360-17) and put it at the
right location on the plot.  You can easily do the modulo operation
yourself on the values in bx:

  let modbx = if bx lt 0 then 360+bx else bx
  polygon/line/over modbx, by

Emilie Vanvyve wrote:

Thanks for the answers I got to my Friday questions! With them, I could finally find an "enough-simple-according-to-me" way to solve my little problem (I agree it is indeed easier to write to/read from a file).
But I now encounter another one when I use POLYGON when a region has been defined: the polygon is not plotted as soon as I restrict the x and/or y-axis values (with: set region, /x=...:..., /y=...:...), otherwise it is plotted.
It may be comprehensible, but I do not know how to put up with that.

Briefly, I do within a script:

set region/x=31.7W:33.7E/y=32.5N:64.9N !Europe instead of whole world
shade my_var
polygon/line/over bx,by


shade/x=31.7W:33.7E/y=32.5N:64.9N my_var !Europe instead of whole world
polygon/line/over bx,by

where bx and by are both 1-D arrays, containing resp. longitude and latitude values of a shape I wish to draw on the plot.
They are e.g. (read from the box.dat file):

yes? list bx, by
DATA SET: ./box.dat
X: 0.5 to 348.5
Column 1: BX
Column 2: BY
1 / 1: -17.00 32.53
2 / 2: -17.08 32.87
3 / 3: -17.17 33.21
4 / 4: -17.26 33.55
5 / 5: -17.35 33.89
344 / 344: -15.38 32.81
345 / 345: -15.78 32.74
346 / 346: -16.19 32.67
347 / 347: -16.59 32.60
348 / 348: -17.00 32.53

I suspect the problem to be directly linked to the restriction I impose on x and/or y-axis values, when I define the region. Those restrictions might in fact be also applied to bx and by. Their index 1 to 348 seem to be understood as longitudes.
I tried to give the bx and by values according another axis: polygon/line/over zsequence(bx), zsequence(by)
but it did not work.

What's the solution...?
Thanks in advance for any suggestion!


Physicist, PhD student

Université catholique de Louvain (UCL)
Institut d'astronomie et de géophysique G. Lemaître (ASTR)
Chemin du Cyclotron, 2
1348 Louvain-la-Neuve (Belgium)
Phone : +32-(0)10-473300
Fax : +32-(0)10-474722
E-mail : vanvyve@astr.ucl.ac.be
Web : www.astr.ucl.ac.be

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