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Hi Nicolas,
Yes, sometimes it's useful to do a SHOW FUNCTION/DETAILS to see
how the result depends on the grids of the arguments. The result
mask you're defining will have the x and y axes of the first
argument, and the other arguments are just lists.
Most often for function calls, it's best to specify any ranges as
a context in square brackets right in the function call. I don't
know what mihght have been going wrong in your original example,
but if you had a global region defined using SET REGION that could
throw things off.
yes? show func/details pt_in_poly
PT_IN_POLY(A,XVERT,YVERT)
Return -1 outside, 0 if on edge, 1 if inside polygon
Axes of result:
X: inherited from argument(s)
Y: inherited from argument(s)
Z: NORMAL (no axis)
T: NORMAL (no axis)
E: NORMAL (no axis)
F: NORMAL (no axis)
A: Variable on the XY grid and region to be tested
(FLOAT)
Influence on output axes:
X: passed to result grid
Y: passed to result grid
Z: no influence (indicate argument limits with
"[]")
T: no influence (indicate argument limits with
"[]")
E: no influence (indicate argument limits with
"[]")
F: no influence (indicate argument limits with
"[]")
XVERT: X-coordinates of vertices of polygon (FLOAT)
Influence on output axes:
X: no influence (indicate argument limits with
"[]")
Y: no influence (indicate argument limits with
"[]")
Z: no influence (indicate argument limits with
"[]")
T: no influence (indicate argument limits with
"[]")
E: no influence (indicate argument limits with
"[]")
F: no influence (indicate argument limits with
"[]")
YVERT: Y-coordinates of vertices of polygon (FLOAT)
Influence on output axes:
X: no influence (indicate argument limits with
"[]")
Y: no influence (indicate argument limits with
"[]")
Z: no influence (indicate argument limits with
"[]")
T: no influence (indicate argument limits with
"[]")
E: no influence (indicate argument limits with
"[]")
F: no influence (indicate argument limits with
"[]")
On 3/26/2019 11:30 AM, Nicolas Freychet
wrote:
Hi Ansley,
Yes it does show the right boundary. Actually I found a
solution by specifying the i/j limits of the var in the
definition (I think because I used "dimensional" lists to
define the polygon, it was somehow inconsistent with dimension
of the variable). So something like that works:
let xp=LON[d=7,i=1:735178]
let yp=LAT[d=7,i=1:735178]
let mask = if
pt_in_poly(Tmax[d=1,l=1,i=1:350,j=1:95],xp,yp) gt 0 then 1
Cheers,
Nicolas
Hi
Nicolas,
As a check of your definition, does a plot of the points
PLOT/VS/LINE xp, yp
show the outline of the boundary you want?
On 3/25/2019 4:18 AM, Nicolas Freychet wrote:
> Dear Ferret users,
>
> I'm trying to create a mask for a country, following this
discussion:
> https://www.pmel.noaa.gov/maillists/tmap/ferret_users/fu_2012/msg00019.html
>
> I managed to have a netcdf file with all lon/lat
coordinate to define
> a polygon of the country as in the discussion, but now I
am not sure
> how to apply it to mask my data.
> The pt_in_poly function
> (https://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/appendix-a-external-functions/pt_in_poly)
> requires to define a table of xp/yp. I tried to do
something like:
>
> let xp=LON[d=7,i=1:735178]
> let yp=LAT[d=7,i=1:735178]
> let mask = if pt_in_poly(Tmax[d=1,l=1],xp,yp) gt 0 then 1
>
> But it doesn't seem to work. I think it's the way I
define xp/yp that
> is wrong, but I don't know how to make a table {} from a
coordinate.
> Any idea?
>
> Cheers,
> Nico
>
--
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Nicolas Freychet
PDRA, School of Geosciences
University of Edinburgh
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