# [ncl-talk] NCL Plotting

Dennis Shea shea at ucar.edu
Wed Feb 14 07:43:20 MST 2018

```I suggest that you look at the NCL examples page;

http://www.ncl.ucar.edu/Applications/

Then look under "Vectors"

-----------------------------------
Two ways to 'thin' vectors:

(a) As noted by Barry: use NCL array syntax. This hard-wires a specific
subset.
plotB  = gsn_csm_vector(wks,u_new*(::4,:**:4)*,v_new*(::4,::4)*
,vecres)
Generally, this is
plotB  = gsn_csm_vector(wks,u_new(::ny,:
:mx),v_new(::ny,::mx),vecres)
Note that 'ny' need not equal 'mx'
plotB  = gsn_csm_vector(wks,u_new(::4,::2),v_new(::4,::2),vecres)

(b) If you click on "Vectors"
http://www.ncl.ucar.edu/Applications/vector.shtml

Within the top 'preamble', there is the comment:

Important resources for controlling the length, *density,* direction, and
style of vectors:

*[snip]*

*vcMinDistanceF*
<http://www.ncl.ucar.edu/Document/Graphics/Resources/vc.shtml#vcMinDistanceF>
- *set to small value to thin the vectors*.  <%%%%%%%%%%%%%%%%%

Then, click on "resources" at the top of the page and search for
"vcMinDistanceF". This will show you all the examples that use this
resource.

This is an 'even better' way to thin vectore.

*vcMinDistanceF*
<http://www.ncl.ucar.edu/Document/Graphics/Resources/vc.shtml#vcMinDistanceF>
WRF_2d_3.ncl <http://www.ncl.ucar.edu/Applications/Scripts/WRF_2d_3.ncl>
(WRF 2D data <http://www.ncl.ucar.edu/Applications/wrf2d.shtml#ex3>)
WRF_2d_4.ncl <http://www.ncl.ucar.edu/Applications/Scripts/WRF_2d_4.ncl>
(WRF 2D data <http://www.ncl.ucar.edu/Applications/wrf2d.shtml#ex4>)
WRF_lc_7.ncl <http://www.ncl.ucar.edu/Applications/Scripts/WRF_lc_7.ncl>
(WRF lambert conformal projections
<http://www.ncl.ucar.edu/Applications/wrflc.shtml#ex7>)
WRF_lc_8.ncl <http://www.ncl.ucar.edu/Applications/Scripts/WRF_lc_8.ncl>
(WRF lambert conformal projections
<http://www.ncl.ucar.edu/Applications/wrflc.shtml#ex8>)
barb_1.ncl <http://www.ncl.ucar.edu/Applications/Scripts/barb_1.ncl> (wind
barbs <http://www.ncl.ucar.edu/Applications/barb.shtml#ex1>)
barb_2.ncl <http://www.ncl.ucar.edu/Applications/Scripts/barb_2.ncl> (wind
barbs <http://www.ncl.ucar.edu/Applications/barb.shtml#ex2>)
barb_3.ncl <http://www.ncl.ucar.edu/Applications/Scripts/barb_3.ncl> (wind
barbs <http://www.ncl.ucar.edu/Applications/barb.shtml#ex3>)
ce_4.ncl <http://www.ncl.ucar.edu/Applications/Scripts/ce_4.ncl>
(cylindrical
equidistant projections
<http://www.ncl.ucar.edu/Applications/cylineq.shtml#ex4>)
coamps_2.ncl <http://www.ncl.ucar.edu/Applications/Scripts/coamps_2.ncl>
(COAMPS <http://www.ncl.ucar.edu/Applications/coamps.shtml#ex2>)
coamps_3.ncl <http://www.ncl.ucar.edu/Applications/Scripts/coamps_3.ncl>
(COAMPS <http://www.ncl.ucar.edu/Applications/coamps.shtml#ex3>)
coamps_5.ncl <http://www.ncl.ucar.edu/Applications/Scripts/coamps_5.ncl>
(COAMPS <http://www.ncl.ucar.edu/Applications/coamps.shtml#ex5>)
coamps_6.ncl <http://www.ncl.ucar.edu/Applications/Scripts/coamps_6.ncl>
(COAMPS <http://www.ncl.ucar.edu/Applications/coamps.shtml#ex6>)
dataonmap_2.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/dataonmap_2.ncl> (Plotting
data on a map
<http://www.ncl.ucar.edu/Applications/plot_data_on_map.shtml#ex2>)
dataonmap_4.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/dataonmap_4.ncl> (Plotting
data on a map
<http://www.ncl.ucar.edu/Applications/plot_data_on_map.shtml#ex4>)
dataonmap_native_4.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/dataonmap_native_4.ncl> (Plotting
data on a map
<http://www.ncl.ucar.edu/Applications/plot_data_on_map.shtml#ex4>)
dataonmap_nonnative_4.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/dataonmap_nonnative_4.ncl>
(Plotting
data on a map
<http://www.ncl.ucar.edu/Applications/plot_data_on_map.shtml#ex4>)
epflux_1.ncl <http://www.ncl.ucar.edu/Applications/Scripts/epflux_1.ncl>
(EPflux <http://www.ncl.ucar.edu/Applications/epflux.shtml#ex1>)
epflux_2.ncl <http://www.ncl.ucar.edu/Applications/Scripts/epflux_2.ncl>
(EPflux <http://www.ncl.ucar.edu/Applications/epflux.shtml#ex2>)
era40_2.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/era40_2.ncl> (ERA40
data <http://www.ncl.ucar.edu/Applications/era40.shtml#ex2>)
global_nogaps_vec.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/global_nogaps_vec.ncl>
global_nogaps_vec_con.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/global_nogaps_vec_con.ncl>
global_nogaps_vec_con_panel.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/global_nogaps_vec_con_panel.ncl>
global_nogaps_vec_panel.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/global_nogaps_vec_panel.ncl>
godas_2.ncl <http://www.ncl.ucar.edu/Applications/Scripts/godas_2.ncl> (
GODAS <http://www.ncl.ucar.edu/Applications/godas.shtml#ex2>)
godas_4.ncl <http://www.ncl.ucar.edu/Applications/Scripts/godas_4.ncl> (
GODAS <http://www.ncl.ucar.edu/Applications/godas.shtml#ex4>)
hycom_con_vec.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/hycom_con_vec.ncl>
ice_2.ncl <http://www.ncl.ucar.edu/Applications/Scripts/ice_2.ncl> (CESM
ice model <http://www.ncl.ucar.edu/Applications/ice.shtml#ex2>)
lat2pop_2.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/lat2pop_2.ncl> (lat/lon to POP
<http://www.ncl.ucar.edu/Applications/lat2pop.shtml#ex2>)
lcnative_4.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/lcnative_4.ncl> (native
lambert conformal <http://www.ncl.ucar.edu/Applications/lcnative.shtml#ex4>)
lcnative_5.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/lcnative_5.ncl> (native
lambert conformal <http://www.ncl.ucar.edu/Applications/lcnative.shtml#ex5>)
lcnative_overlay_5.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/lcnative_overlay_5.ncl>
mjoclivar_16.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/mjoclivar_16.ncl> (MJO
climate variability
<http://www.ncl.ucar.edu/Applications/mjoclivar.shtml#ex16>)
newcolor_8.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/newcolor_8.ncl> (new 32-bit
color capabilities
<http://www.ncl.ucar.edu/Applications/rgbacolor.shtml#ex8>)
nldas_01.ncl <http://www.ncl.ucar.edu/Applications/Scripts/nldas_01.ncl>
(NLDAS-GLDAS <http://www.ncl.ucar.edu/Applications/nldas_gldas.shtml#ex01>)
nlom_1.ncl <http://www.ncl.ucar.edu/Applications/Scripts/nlom_1.ncl> (
NLOM <http://www.ncl.ucar.edu/Applications/nlom.shtml#ex1>)
nlom_vec_con.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/nlom_vec_con.ncl>
polar_7.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/polar_7.ncl> (polar
stereographic projection
<http://www.ncl.ucar.edu/Applications/polar.shtml#ex7>)
polar_8.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/polar_8.ncl> (polar
stereographic projection
<http://www.ncl.ucar.edu/Applications/polar.shtml#ex8>)
pop2lat_2.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/pop2lat_2.ncl> (POP to lat/lon
<http://www.ncl.ucar.edu/Applications/pop2lat.shtml#ex2>)
popscal_4.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/popscal_4.ncl> (POP scalars
<http://www.ncl.ucar.edu/Applications/popscal.shtml#ex4>)
popvec_2.ncl <http://www.ncl.ucar.edu/Applications/Scripts/popvec_2.ncl>
(POP vectors <http://www.ncl.ucar.edu/Applications/popvec.shtml#ex2>)
popvec_3.ncl <http://www.ncl.ucar.edu/Applications/Scripts/popvec_3.ncl>
(POP vectors <http://www.ncl.ucar.edu/Applications/popvec.shtml#ex3>)
popvec_4.ncl <http://www.ncl.ucar.edu/Applications/Scripts/popvec_4.ncl>
(POP vectors <http://www.ncl.ucar.edu/Applications/popvec.shtml#ex4>)
roms_5.ncl <http://www.ncl.ucar.edu/Applications/Scripts/roms_5.ncl> (
ROMS <http://www.ncl.ucar.edu/Applications/roms.shtml#ex5>)
veceff_4.ncl <http://www.ncl.ucar.edu/Applications/Scripts/veceff_4.ncl>
(vector effects <http://www.ncl.ucar.edu/Applications/veceff.shtml#ex4>)
vector_3.ncl <http://www.ncl.ucar.edu/Applications/Scripts/vector_3.ncl>
(vector plots <http://www.ncl.ucar.edu/Applications/vector.shtml#ex3>)
vector_4.ncl <http://www.ncl.ucar.edu/Applications/Scripts/vector_4.ncl>
(vector plots <http://www.ncl.ucar.edu/Applications/vector.shtml#ex4>)
vector_5.ncl <http://www.ncl.ucar.edu/Applications/Scripts/vector_5.ncl>
(vector plots <http://www.ncl.ucar.edu/Applications/vector.shtml#ex5>)
wind_1.ncl <http://www.ncl.ucar.edu/Applications/Scripts/wind_1.ncl>
(divergent
and rotational wind components
<http://www.ncl.ucar.edu/Applications/wind.shtml#ex1>)
wind_2.ncl <http://www.ncl.ucar.edu/Applications/Scripts/wind_2.ncl>
(divergent
and rotational wind components
<http://www.ncl.ucar.edu/Applications/wind.shtml#ex2>)
wind_3.ncl <http://www.ncl.ucar.edu/Applications/Scripts/wind_3.ncl>
(divergent
and rotational wind components
<http://www.ncl.ucar.edu/Applications/wind.shtml#ex3>)
wind_4.ncl <http://www.ncl.ucar.edu/Applications/Scripts/wind_4.ncl>
(divergent
and rotational wind components
<http://www.ncl.ucar.edu/Applications/wind.shtml#ex4>)

*vcMinFracLengthF*
<http://www.ncl.ucar.edu/Document/Graphics/Resources/vc.shtml#vcMinFracLengthF>
newcolor_7.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/newcolor_7.ncl> (new 32-bit
color capabilities
<http://www.ncl.ucar.edu/Applications/rgbacolor.shtml#ex7>)
newcolor_8.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/newcolor_8.ncl> (new 32-bit
color capabilities
<http://www.ncl.ucar.edu/Applications/rgbacolor.shtml#ex8>)
overlay_6.ncl
<http://www.ncl.ucar.edu/Applications/Scripts/overlay_6.ncl> (Overlays
<http://www.ncl.ucar.edu/Applications/overlay.shtml#ex6>)
unique_2.ncl <http://www.ncl.ucar.edu/Applications/Scripts/unique_2.ncl>
(unique plots <http://www.ncl.ucar.edu/Applications/unique.shtml#ex2>)
unique_4.ncl <http://www.ncl.ucar.edu/Applications/Scripts/unique_4.ncl>
(unique plots <http://www.ncl.ucar.edu/Applications/unique.shtml#ex4>)
veceff_1.ncl <http://www.ncl.ucar.edu/Applications/Scripts/veceff_1.ncl>
(vector effects <http://www.ncl.ucar.edu/Applications/veceff.shtml#ex1>)
veceff_2.ncl <http://www.ncl.ucar.edu/Applications/Scripts/veceff_2.ncl>
(vector effects <http://www.ncl.ucar.edu/Applications/veceff.shtml#ex2>)
veceff_3.ncl <http://www.ncl.ucar.edu/Applications/Scripts/veceff_3.ncl>
(vector effects <http://www.ncl.ucar.edu/Applications/veceff.shtml#ex3>)
veceff_4.ncl <http://www.ncl.ucar.edu/Applications/Scripts/veceff_4.ncl>
(vector effects <http://www.ncl.ucar.edu/Applications/veceff.shtml#ex4>)

On Wed, Feb 14, 2018 at 12:24 AM, Barry Lynn <barry.h.lynn at gmail.com> wrote:

> Here is how you do it.
>
>   vecres                  = True            ; vector only resources
>
>   vecres at gsnDraw          = False           ; don't draw
>
>   vecres at gsnFrame         = False           ; don't advance frame
>
>   vecres at vcGlyphStyle     = "CurlyVector"   ; curly vectors
>
>   vecres at vcRefMagnitudeF  = 20              ; define vector ref mag
>
>   vecres at vcRefLengthF     = 0.045           ; define length of vec ref
>
>   vecres at gsnRightString   = " "             ; turn off right string
>
>   vecres at gsnLeftString    = " "             ; turn off left string
>
>   vecres at tiXAxisString    = " "             ; turn off axis label
>
>   vecres at vcRefAnnoOrthogonalPosF = -0.17    ; move ref vector into  plot
>
>
>   vecres at gsnAddCyclic          = False          ; we will manually zoom
> in.
>
>   plotB  = gsn_csm_vector(wks,u_new(::4,::4),v_new(::4,::4),vecres)
>
> Then, you can overlay it onto another plot like temperature.
>
> panres = True
>
> panres at gsnMaximize = True
>
> panres at gsnPanelRight = 0.98
>
> panres at gsnPanelLeft  = 0.02
>
> panres at gsnPaperOrientation="Portrait"
>
> overlay(plot,plotB)
>
> gsn_panel(wks,plot,(/1,1/),panres)
>
>
> On Wed, Feb 14, 2018 at 6:53 AM, Ankita Sharma <ankita at iiserb.ac.in>
> wrote:
>
>> ​​How to use "skip 4" in NCL? or How to skip vectors into grids?
>>
>> _______________________________________________
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>>
>>
>
>
> --
> Barry H. Lynn, Ph.D
> Senior Lecturer,
> The Institute of the Earth Science,
> The Hebrew University of Jerusalem,
> Givat Ram, Jerusalem 91904, Israel
> Tel: 972 547 231 170
> Fax: (972)-25662581
>
> C.E.O, Weather It Is, LTD
> Weather and Climate Focus
> http://weather-it-is.com
> Jerusalem, Israel
> Local: 02 930 9525
> Cell: 054 7 231 170
> Int-IS: x972 2 930 9525
> US 914 432 3108 <(914)%20432-3108>
>
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