Re: Contours on a Gaussian grid

[hankin@xxxxxxxxxxxxxxxxxxx (Steve Hankin)]

On Sep 5,  1:22pm, beland@cerca.umontreal.ca wrote:
> Subject: Contours on a Gaussian grid
> Hello,
>
> I am trying to do a contour or shade plot of data that is on a Gaussian
> grid.  This grid has the latitude circles that are not exactly equally
> spaced.  How can I specify to ferret each latitude on the grid ?  I see
> two methods to accomplish this, although I do not know if ferret is made
> to do them:
>
> 1- contour the data as if it was regularly spaced but draw the axis tics
> and labels unequally spaced;
>
> 2- stretch the plot so that I can have a regular latitude axis, maybe by
> regridding.
>
> Any help appreciated.
>
> --
> Michel Beland                 beland@CERCA.UMontreal.CA
> professionnel de recherche    tel: (514)369-5223  fax: (514)369-3880
> CERCA (CEntre de Recherche en Calcul Applique)
> 5160, boul. Decarie, bureau 400(423), Montreal (Quebec), Canada, H3X 2H9
>-- End of excerpt from beland@cerca.umontreal.ca

=====================================================================

Hi Michel,

I assume that your data is in an ASCII file.

What I don't know from your message is whether you have the latitude locations
in that file or whether you know them analytically, or whatever ...

If I'm understanding the problem correctly, the solution will be is to make
sure that the grid upon which your variable is defined has the correct
(unequally spaced) Y axis by using "DEFINE AXIS/FROM_DATA ...".

Lets start at the solution at the point that you have the latitude locations
(by whatever means) in a Ferret variable called "lats". Then simply use:

-------

	DEFINE AXIS/X=lo:hi:delta xlongs
	DEFINE AXIS/Y/FROM_DATA/NAME=ylats lats	  ! using the values of "lats"
	DEFINE GRID/X=xlongs/Y=ylats gg
	FILE/var=myvar/grid=gg mydata.dat
	SET VARIABLE/TITLE="my title"/UNITS="some units" myvar

	SHADE myvar

-------

	Happy Ferreting - steve



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