[ncl-talk] Problem of using "get_isolines"

[Mary Haley]

Hi,

We were looking into this problem using a different example, and seeing
some odd results.

Is it possible for you to provide us with the pt.nc file?

You can use our ftp, if the file is not too large:

http://www.ncl.ucar.edu/report_bug.shtml#HowToFTP

Thanks,

--Mary


On Tue, May 30, 2017 at 8:17 PM, 王淼 <miaowang2015 at pku.edu.cn> wrote:

> Hi Ncl Talk,
>    I used get_isolines to get the points that define a contour line .When
> I printed the longitude of these points ,  the distribution of the
> longitude wasn't the same(gonna show in the following example) ,may be
> [0~-360] or [20~-340],etc. I have expected the function may return the
> longitude as [0~360] or [-180~180]. I googled it ,but didn't help.I still
> don't know what caused the effect, so I ask you for help. Thanks!
>
> Here is the code and resluts:
>
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/contrib/cd_string.ncl"
>
> begin
>
> f1=addfile("pt.nc","r")         ;pt(time,lat,lon)
> pt=short2flt(f1->pt)
> pt=lonFlip(pt)                  ;lon=0~360degrees
>
> n=dimsizes(pt&time)
>
>
>   wks = gsn_open_wks("pdf","sypt_all")
>
>   res                      = True
>   res at gsnDraw              = False
>   res at gsnFrame             = False
>
>   res at cnFillOn             = False
>   res at cnLinesOn            = True
>
>   res at cnLevelSelectionMode   = "ExplicitLevels"
>   res at cnLevels              = (/350,360/)
>
>
>   res at mpMinLatF            = 0
>   res at mpCenterLonF         =180
> res at trGridType = "TriangularMesh"
>
>
> do i = 0, n-1                                           ;time
>     plot=gsn_csm_contour_map_ce(wks, pt(i,:,:), res)
>
>      isolines = get_isolines(plot at contour,"plot")
>
>     do j= 0, ListCount(isolines) - 1
>       iso := isolines[j]
>
>       idx=maxind(iso at n_points)
>       b = iso at start_point(idx)
>       e = b + iso at n_points(idx) - 1
>       y := iso(0,b:e)
>       x := iso(1,b:e)                   ;y=lat,x=lon
>       print(x)
>     end do
> end do
> end
>
> result1 result2
> 0 0
> -1.8 -1.3
> -2.5 -2.5
>      …      …
> -358.9 -339.8
> -359.7 -340
> -360      …
> 20
> 18.6
>      …
> 2.5
> 0.5
> 0
>
>
>
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