Re: Plotting partial data

See:

http://www.ncl.ucar.edu/Document/Functions/Contributed/region_ind.shtml

On 03/30/2010 11:03 AM, Tong Qi wrote:
> Dennis,
>
> Most of the data fields I work with do not contain the time dimension.
> Assuming the simple case of YDim and XDim which are shared by the
> Latitude/Longitude and data, if I do what you have suggested (which is
> similar to my current method), the range will be properly zoomed in on,
> however all of the values of x will be read, rather than just the area
> of interest.
>
> I'm wondering if there is some way to restrict reading only the values
> in the zoomed in range for x automatically.
>
> Let's say x(YDim, XDim), and YDim ranges from 0-179, XDim ranges from
> 0-359.
> The geolocation fields of Latitude(YDim, XDim) and Longitude(YDim, XDim)
> are mapped to x by:
> x@lat2d=Latitude
> x@lon2d=Longitude
>
> If I want to focus only on the western hemisphere, for example, I would
> use res@mpMaxLonF=0 and
> plot=gsn_csm_contour_map_ce(wks,x,res)
>
> The resultant plot would only have the western hemisphere, but all of
> the values of x were read. A solution I found was to limit x:
>
> plot=gsn_csm_contour_map_ce(wks, x(:,0:179), res)
>
> This limit is easily found because there is a simple mapping from the
> latitude/longitude to YDim and XDim. However, if I'm interested in a
> smaller area that has different latS/latN/lonE/lonW, the mappings are
> not so easily found.
>
>
>
> On Mon, Mar 29, 2010 at 9:50 PM, Dennis Shea <shea@ucar.edu
> <mailto:shea@ucar.edu>> wrote:
>
> You need to be more specific.
>
> say x(time,lat,lon) ... the following may work for you
>
> latS = -20
> latN = 50
> lonE = 30
> lonW = 110
>
> res@mpMinLatF = latS ; range to zoom in on
> res@mpMaxLatF = latN
> res@mpMinLonF = lonE
> res@mpMaxLonF = lonW
>
> res@mpCenterLonF = (lonE+lonW)*0.5 ; optional
> res@pmTickMarkDisplayMode = "Always"; use NCL default lat/lon labels
>
> do nt=0,ntim-1
> plot = gsn_csm_contour_map_ce(wks,x(nt,:,:), res)
> end do
>
>
> Tong Qi wrote:
> > Hello,
> >
> > I was wondering if there is any way for NCL to automatically
> filter out
> > parts of a plotted data field when only a certain subset of the
> data is
> > plotted. For example, if I plot only the western hemisphere vs. the
> > entire globe, since NCL was assigned the full data, it will
> adjust its
> > labels to include all values from the entire globe, even if they
> are not
> > present in the area of interest. I know one way is to first look
> at the
> > data, then assign only the subset that I am interested in, such as
> >
> > data=file->data(0:179,:)
> >
> > to correspond with
> >
> > res@mpMaxLonF=0
> >
> > This would ensure that values outside of the area of interest are not
> > included in the plot, but the situation becomes tricky if the
> file uses
> > non-standard latitude/longitude mappings and I want to subset a more
> > precise area rather than just a hemisphere. I am hoping there is some
> > sort of automatic solution for subset plots.
> >
> > Thanks,
> > -Tong
> >
> >
> >
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-- 
======================================================
Dennis J. Shea                  tel: 303-497-1361    |
P.O. Box 3000                   fax: 303-497-1333    |
Climate Analysis Section                             |
Climate & Global Dynamics Div.                       |
National Center for Atmospheric Research             |
Boulder, CO  80307                                   |
USA                        email: shea 'at' ucar.edu |
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