Hi
Yes, I thought that was probably what you were asking. One way to do
this is with three masks that can be added:
let mnorth = if yy gt 23 then 2 else 0
let msouth = if yy lt -23 then 3 else 0
let mtropic = if (msouth + mnorth) EQ 0 then 1
else 0
let mask = msouth + mnorth + mtropic
! as a check on what you've defined:
let xzero = 0*x[gx=xvar]
shade/lev=3 mask + xzero
Which is probably what you're thinking of with intermediate
variables. It keeps things reasonably simple at the expense of extra
command lines.
Then you can do things like this
let topic_data = if mask eq 1 then mask* myvar
...
Ansley
David Wang wrote:
Hi Ansley,
Thanks for asking. Let's me elaborate it. I'd like to define a few
regional masks for an ocean model so that I can keep monitoring
regional diagnostics without dumping 3d fields when unnecessary. This
is by tagging each region with an unique index (number) on a single
horizontal field. For the sake of simplicity, let's say I need three
masks: tropical ocean (1), north ocean (2), and south ocean (3). In
Ferret, I would have:
let yy = y[gy=myvar]
let mask = if yy gt 23.5 then 2 elif yy lt -23.5 then 3 else 1
where myvar is an arbitrary 2d field on the model grid.
I understand one can definitely break down the above definition into
two steps using an intermediate variable. But this becomes increasingly
awkward when the number of regions increases.
I could miss something obvious. If so, please enlighten me.
Thanks,
D.
On Fri, Mar 27, 2009 at 12:04 PM, Ansley
Manke <Ansley.B.Manke@xxxxxxxx>
wrote:
Hi
David,
Can you write out some Ferret-like commands that show the syntax you're
thinking of? Are you trying to define a variable using a number of
cases? Often there are reasonable alternatives to the way one first
thinks of doing something.
Ansley
David Wang wrote:
Hi Ferreters,
Well, I may sound pretty greedy. But is there a plan to extend the
IF-THEN-ELSE logic to some kind of IF-THEN-ELIF-ELSE logic? It would be
quite useful for multi-region masking. (Note: I'm not talking about
conditional execution, which does have ELIF)
Thanks,
D.
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life grows, death doesn't. there is no dress rehearsal.
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