[ncl-talk] add color dots to map

[Yun Yue]

Thank you Adam,

I found another way to get the plot. But I appreciate your ideas here. Thanks very much.

Yun

________________________________
From: Adam Phillips <asphilli at ucar.edu>
Sent: Friday, March 6, 2015 12:09
To: Yun Yue
Cc: ncl-talk at ucar.edu
Subject: Re: [ncl-talk] add color dots to map

Hi Yun,
Please always include ncl-talk on your replies so that other ncl-talk folks can assist and also so the conversation gets saved in the ncl-talk archives to assist future NCL users.

As my initial suggestion didn't solve the issue I created a sample script that used your code snippet and tried to get it to do what you want. The script and resulting graphics are attached.

I saw two issues that needed addressing:
1) Unless you created your own custom colormap or mistyped, there isn't a colormap named WhAqGrYeOrReVi200. For my test case I switched to using BkBlAqGrYeOrReViWh200.
2) The GetFillColor documentation states that the function is deprecated, and to use either get_color_rgba or get_color_index. GetFillColor assigns colors based on a scalar field, but uses the colors in the retrieved colormap sequentially. For example, if you set up your cnLevels array = (/5,10,15,20,25,30/), and are using the BkBlAqGrYeOrReViWh200 colormap, all points less than 5 will be colored index 2 here:
http://www.ncl.ucar.edu/Document/Graphics/ColorTables/BkBlAqGrYeOrReViWh200.shtml

All points greater than or equal to 5 and less than 10 will be colored index 3, and so on up to index 7. For this colormap, all those indices look black.

What I think you want to do is to use get_color_index instead of GetFillColor, as get_color_index assigns the colors in a fashion similar to the manner that NCL spans colormaps for color-filled graphics. See the documentation here:
http://www.ncl.ucar.edu/Document/Functions/Built-in/get_color_index.shtml

Hope that helps!
Adam

begin

x = ispan(190,290,20)
y = ispan(25,67,6)
pmvalue = ispan(2,32,5)

wks = gsn_open_wks("png", "overlay")
gsn_define_colormap(wks,"BkBlAqGrYeOrReViWh200")
res = True
res at gsnDraw = False
res at gsnFrame = False
res at mpFillOn = False
res at mpOutlineOn = True
res at mpLimitMode = "LatLon"
res at mpMinLatF = 20.
res at mpMaxLatF = 75.
res at mpMinLonF = 180.
res at mpMaxLonF = 300.

res at mpCenterLonF = 240.
plot = gsn_csm_map(wks,res)
cmap      = gsn_retrieve_colormap(wks)
cnLevels = (/5,10,15,20,25,30/)
res_poly = True
res_poly at gsMarkerIndex = 16
res_poly at gsMarkerSizeF = 10
do i = 0, dimsizes(x)-1
res_poly at gsMarkerColor = get_color_index("BkBlAqGrYeOrReViWh200",cnLevels, pmvalue(i))
print("Value = "+pmvalue(i)+" "+res_poly at gsMarkerColor)
dum = gsn_add_polymarker(wks, plot, x(i), y(i), res_poly)
str1  = unique_string("dum")
plot@$str1$=dum
end do
draw (plot)
frame(wks)
end


On Thu, Mar 5, 2015 at 3:53 PM, Yun Yue <yunyue at huskers.unl.edu<mailto:yunyue at huskers.unl.edu>> wrote:


Hi NCL users,

I'm trying to plot observation data to model simulated data map. I think I should use gsn_add_polymarker to overlay them. But for the @gsMarkerColor, I want use the same color for plotting simulated data map, so I tried to use code like the following. But I got black dots on the map. Can somebody help me to solve this? Thank you very much.

Yun

wks = gsn_open_wks("x11", "overlay")

gsn_define_colormap(wks,"WhAqGrYeOrReVi200")

cmap      = gsn_retrieve_colormap(wks)

cnLevels = (/5,10,15,20,25,30/)

res_poly = True

res_poly at gsMarkerIndex = 16

res_poly at gsMarkerSizeF = 10

do i = 0, station_numb

res_poly at gsMarkerColor = GetFillColor(cnLevels, cmap, pmvalue(i))

dum = gsn_add_polymarker(wks, plot, x, y, res_poly)
str1  = unique_string("dum")
plot@$str1$=dum
end do
draw (plot)





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--
Adam Phillips
Associate Scientist,  Climate and Global Dynamics Division, NCAR
www.cgd.ucar.edu/staff/asphilli/<http://www.cgd.ucar.edu/staff/asphilli/>   303-497-1726

<http://www.cgd.ucar.edu/staff/asphilli>
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