Hi Derek,
There are still some things you could do in Ferret even if you can't
recover the complete grid from wherever this data came from. You could
read in the longitudes, latitudes, and values into three 1-dimensional
variables and use one of the SCAT2GRID* functions to put it onto a
rectilinear grid.
Ansley
Derek Tsui wrote:
Yes. The data I am working with has missing points. I believe
they are missing data but instead of flagging them, the points
were taken out of the file. So it is not a well-defined grid.
Derek
On Thu, May 7, 2009 at 5:55 PM, Ansley Manke
<Ansley.B.Manke@xxxxxxxx>
wrote:
Hi Derek,
I'm not sure how that could happen. For a well-defined polar
stereographic grid, there has to be a complete set of longitudes and
latitudes. There might be missing values for the data field, and those
should have a missing-data flag, some particular value that marks that
as bad data. Maybe what you're starting with has just left out those
points?
Derek Tsui wrote:
Thanks Ansley. I was wondering what would I do then if nx
and ny isn't fixed in the data? When there is missing data.
For example, xindex = 1, yindex = 1:140 , but xindex = 2, yindex = 1:135
Derek
On Tue, May 5, 2009 at 6:17 PM, Ansley
Manke <Ansley.B.Manke@xxxxxxxx>
wrote:
Hi Derek,
Your polar projection has coordinate data which is 2-dimensional, that
is the longitudes and latitudes are defined on i,j index coordinate
grid. At each i,j index pair there is a longitude, a latitude, and the
value. Once you've accessed this data in Ferret, you'll use the
curvilinear form of graphics calls to visualize the data.
What I would do is just write these three things to your ascii file,
one longitude, latitude, value per record, with i varying fastest.
Then define a grid which has x and y axes that are just the index
values of the curvilinear coordinate variables:
yes? let nx = 140 ! or whatever the number of
values is for your grid
yes? let ny = 80
yes? define axis/x=1:`nx`:1 xindex
yes? define axis/y=1:`ny`:1 yindex
yes? define grid/x=xindex/y=yindex grid_ij
yes? file/var="xlon,ylat,value"/grid=grid_ij myfile.dat
yes? FILL value, xlon, ylat
Derek Tsui wrote:
Sorry I'm not sure if there were a response since I sent
out the question before subscribing.
Thanks,
Derek
---------- Forwarded message
----------
From: Derek Tsui <i.am.mr.sleepyhead@xxxxxxxxx>
Date: Wed, Apr 22, 2009 at 5:07 PM
Subject: reading ascii in polar stereographic projection
To: ferret_users@xxxxxxxx
I have a dataset in polar stereographic projection,
ascii format, that I am trying to load into ferret and plot. It is 3
columns of data. longitutde, latitude, value. I can format it in any
way.
I've tried the general script in the "Reading an ascii file: longitute
latitute variable" thread but it doesn't seem to work in my case.
Any help would be much appreciated.
Thank you,
Derek
|