Hello,
I will answer two questions you sent to me outside of the list.
First, some general comments about interpolation in Ferret.
MODE INTERPOLATE controls whether Ferret interpolates results when
getting data out of a grid. So, for instance, say you have a data
on an axis which is every 10 degrees, such as
define axis/x=0:360:10/units=degrees_east
and you ask Ferret to list data at x=28E. With MODE INTERPOLATE
turned on, Ferret would do a linear interpolation between the data
values at x=20 and x=30 and return that interpolated result. If
MODE INTERPOLATE is off, it would return the data at the nearest
location, x=30.
Interpolating to a grid can mean a couple of different things. For
your data, which is ungridded data with locations lon, lat and data
at lon,lat; we use one of the scat2grid functions, as you show here.
If the data is gridded, then interpolating to another grid is
referred to in the documentation as "regridding". Finally if you
had gridded data, and wanted data at a set of X,Y locations, that
would be "sampling".
Now, about scat2gridgauss_xy. The script you sent earlier needs one
change. You had this:
yes? use wm_20110101.nc
yes? DEFINE AXIS/X=15E:120:10/UNIT=DEGREES xlon
yes? DEFINE AXIS/Y=-60S:30N:10/UNIT=DEGREES ylat
yes? DEFINE GRID/X=xlon/Y=ylat gsnoopy2d
The Y axis definition should not have -60S, but either 60S or -60,
without the S.
yes? use wm_20110101.nc
yes? DEFINE AXIS/X=15E:120:10/UNIT=DEGREES xlon
yes? DEFINE AXIS/Y=60S:30N:10/UNIT=DEGREES ylat
yes? let swhcorgrid = scat2gridgauss_xy (lat, lon,
swhcor, x[gx=xlon], y[gy=ylat], 4,2,4,2)
yes? stat swhcorgrid
SCAT2GRIDGAUSS_XY (LAT, LON, SWHCOR, X[GX=XLON],
Y[GY=YLAT], 4,2,4,2)
LONGITUDE: 10E to 130E
LATITUDE: 65S to 35N
Z: N/A
T: N/A
E: N/A
F: N/A
DATA SET: ./wm_20110101.nc
Total # of data points: 120 (12*10*1*1*1*1)
# flagged as bad data: 40
Minimum value: 0.62119
Maximum value: 5.3594
Mean value: 2.6417 (unweighted average)
Standard deviation: 1.1658
On 2/4/2014 10:55 PM, Selvam G. wrote:
Dear Prof,
I tried another command with scat2gridgauss_xy , In this
Interpolation data points are drawn. please guide me for
Interpolating data points within this region, LON=15:120 and
LAT=-60:30.
yes? let swhcorgrid = scat2gridgauss_xy (lat, lon,
swhcor, x[gx=xlon], y[gy=ylat], 4,2,4,2)
yes? stats swhcorgrid
SCAT2GRIDGAUSS_XY (LAT, LON, SWHCOR,
X[GX=XLON], Y[GY=YLAT], 4,2,4,2)
LONGITUDE: 10E to 130E
LATITUDE: 25N to 65N
Z: N/A
T: N/A
E: N/A
F: N/A
DATA SET: ./wm_20110101.nc
Total # of data points: 48 (12*4*1*1*1*1)
# flagged as bad data: 17
Minimum value: 0.5978
Maximum value: 4.3431
Mean value: 1.6993 (unweighted average)
Standard deviation: 1.3002
yes? let xlon = XSEQUENCE(lon)
yes? let ylat = YSEQUENCE(lat)
yes? let yswhcor = YSEQUENCE(swhcor)
yes? let salinite =
SCAT2GRIDGAUSS_XY(xlon,ylat,yswhcor,x[gx=xlon],y[gy=ylat],2,2,2,2)
yes?
regards,
Selvam G.
From:
"Ansley Manke" <ansley.b.manke@xxxxxxxx>
To: "Selvam G." <gselvam@xxxxxxx>
Cc: "ferret users" <ferret_users@xxxxxxxx>
Sent: Tuesday, February 4, 2014 11:18:17 PM
Subject: Re: [ferret_users] Spatial Trend
Hello,
Your data is organized as lists of longitude, latitude,
time and measurements. You used a good method,
plot/vs/ribbon, to visualize the density and range of the
data.
yes? go basemap x=15:120 y=-60:30
yes?
plot/vs/over/nolab/ribbon/thick/size=0.08/symbol=17/key/LEV=
v LON,LAT,SWHCOR
To interpolate it to a grid, use one of the SCAT2GRID
functions
yes? show function scat2grid*xy
Perhaps the scat2gridgauss_xy function. A note on the
syntax: in your axis definition, the latitude axis should
be one of these:
DEFINE AXIS/Y=60S:30N:10/UNIT=DEGREES ylat
DEFINE AXIS/Y=-60:30:10/UNIT=DEGREES ylat
Not -60S.
-Ansley
On 2/3/2014 7:49 PM, Selvam
G. wrote:
Dear Prof,
I would like to know the ferret command for linear Interpolation. I am dealing with Ifremer altimeter wave data for Indian Ocean.I plotted the map but when the Interpolation command is given the .des file is not shown as it is Interpolated. I am attaching one of my wave data for your consideration. I request your guidance for this Interpolation.
Thanks & regards
Selvam G.
----- Original Message -----
From: "Russ Fiedler" <russell.fiedler@xxxxxxxx>
To: "ferret users" <ferret_users@xxxxxxxx>
Sent: Tuesday, February 4, 2014 3:16:38 AM
Subject: Re: [ferret_users] Spatial Trend
The time units for the trend should correspond to the time axis for your
data. If it's days then you will have to multiply by 365 or 365.25 to
get the trend in terms of years.
Russ
On 03/02/14 23:45, iwlod@xxxxxxxxxxxxxxxxxxx wrote:
I dont think it is that simple - units on slope are way to small
can someone else confirm?
thanks
Simply shade slope.
Sent from my iPhone
On Jan 31, 2014, at 4:17 AM, iwlod@xxxxxxxxxxxxxxxxxxx wrote:
Collective Ferret Wisdom :-)
How do I go from a linear regression line plot (with go regresst) to a
SPATIAL (lat x lon) trend map of say, temperature for the past 20
years?
Thank you
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