Re: [Matplotlib-users] Basemap plotting data on projection
Dear Scott,
I am sorry for giving no reply. Thanks for your answer. I tried it and it
works fine.
best ,
Chao
On Tue, Apr 30, 2013 at 1:21 PM, Scott Sinclair-4 [via matplotlib]
ml-node+s1069221n40977...@n5.nabble.com wrote:
Forgot to send to the list sigh
-- Forwarded message --
From: Scott Sinclair [hidden
email]http://user/SendEmail.jtp?type=nodenode=40977i=0
Date: 30 April 2013 13:20
Subject: Re: [Matplotlib-users] Basemap plotting data on projection
To: ChaoYue [hidden
email]http://user/SendEmail.jtp?type=nodenode=40977i=1
On 29 April 2013 23:32, ChaoYue [hidden
email]http://user/SendEmail.jtp?type=nodenode=40977i=2
wrote:
pdata = np.genfromtxt('pdata.txt')
pdata = np.ma.masked_greater(pdata,1E20)
lonm,latm=m.makegrid(pdata.shape[1],pdata.shape[0])
The problem is here ^^^
The data don't lie on an equally spaced grid in the Mercator
projection, so it doesn't make sense to ask for the lat/lon
coordinates of a grid that is equally spaced in this projection. You
need to determine the *actual* lat/lon coordinates before projecting
them onto the Mercator map and plotting...
Something like this should work (If you can assume that the data are
on an equally spaced grid in Equidistant Cyl projection having the
boundaries specified):
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt
# Set up the Equidistant Cyl projection to determine data locations.
pdata = np.genfromtxt('pdata.txt')
pdata = np.ma.masked_greater(pdata, 1E20)
ny, nx = pdata.shape
cyl_basemap = Basemap(projection='cyl', llcrnrlat=9, urcrnrlat=54.5,
llcrnrlon=74, urcrnrlon=142, lat_ts=20,
resolution='l')
lon, lat = cyl_basemap.makegrid(nx, ny)
# Set up the Mercator projection for plotting.
m = Basemap(projection='merc', llcrnrlat=9, urcrnrlat=54.5,\
llcrnrlon=74, urcrnrlon=142, lat_ts=20, resolution='l')
m.drawcountries()
m.drawcoastlines()
m.drawmapboundary(fill_color='white')
m.drawrivers()
x, y = m(lon, np.flipud(lat))
cs = m.contourf(x, y, pdata)
m.colorbar(cs)
plt.show()
Cheers,
Scott
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Tel: (33) 01 69 08 29 02; Fax:01.69.08.77.16
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Re: [Matplotlib-users] Basemap plotting data on projection
Hi all,
Indeed it's a bit strange, I can reproduce the problem. But when using
'cyl' projection I don't have this issue.
attahced two figures showed the difference.
the tested data is also attached.
complete code is below:
from mpl_toolkits.basemap import Basemap, cm, maskoceans
import matplotlib.pyplot as plt
# set up the Mercator projection
m = Basemap(projection='merc',llcrnrlat=9,urcrnrlat=54.5,\
llcrnrlon=74,urcrnrlon=142,lat_ts=20,resolution='l')
m.drawcountries()
m.drawcoastlines()
m.drawmapboundary(fill_color='aqua')
m.drawrivers()
pdata = np.genfromtxt('pdata.txt')
pdata = np.ma.masked_greater(pdata,1E20)
lonm,latm=m.makegrid(pdata.shape[1],pdata.shape[0])
latm=np.flipud(latm)
lonpro,latpro=m(lonm,latm)
cs = m.contourf(lonpro,latpro,pdata)
m.colorbar(cs)
cheers,
Chao
On Mon, Apr 29, 2013 at 12:53 PM, Ann [via matplotlib]
ml-node+s1069221n40973...@n5.nabble.com wrote:
Dear All,
I am encountering the following problem:
I have some data which I want to plot on a map. Unfortunately, I do not
manage to plot the data according to the shape of the projection! What it
appears to do is to simply plot the data on top of the projection without
taking the actual position (latitude and longitude) into account. However,
this is crucial for my analysis.
Could anybody spot the mistake in my code?
Any suggestion would be of great help!!
THANKS
from mpl_toolkits.basemap import Basemap, cm, maskoceans
import matplotlib.pyplot as plt
# set up the Mercator projection
m = Basemap(projection='merc',llcrnrlat=9,urcrnrlat=54.5,\
llcrnrlon=74,urcrnrlon=142,lat_ts=20,resolution='l')
m.drawcountries()
m.drawcoastlines()
m.drawmapboundary(fill_color='aqua')
m.drawrivers()
parallels = N.arange(0.,81,10.)
labels = [left,right,top,bottom]
m.drawparallels(parallels,labels=[1,0,0,0])
meridians = N.arange(10.,351.,20.)
m.drawmeridians(meridians,labels=[0,0,0,1])
ny=resmat.shape[0] # resmat is the matrix containing the data which I want
o plot.
nx=resmat.shape[1]
#get lat/lons of ny by nx evenly space grid
lons, lats =m.makegrid(nx, ny)
# compute map projection coordinates
x, y= m(lons, lats)
maskdata = maskoceans(lons, lats, resmat, inlands= True, resolution = 'l')
cs = m.contourf(x,y,maskdata,150,cmap=cm.GMT_no_green_r)
plt.show()
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Chao YUE
Laboratoire des Sciences du Climat et de l'Environnement (LSCE-IPSL)
UMR 1572 CEA-CNRS-UVSQ
Batiment 712 - Pe 119
91191 GIF Sur YVETTE Cedex
Tel: (33) 01 69 08 29 02; Fax:01.69.08.77.16
pdata.txt (413K)
http://matplotlib.1069221.n5.nabble.com/attachment/40975/0/pdata.txt
cyl.jpg (540K)
http://matplotlib.1069221.n5.nabble.com/attachment/40975/1/cyl.jpg
merc.jpg (435K)
http://matplotlib.1069221.n5.nabble.com/attachment/40975/2/merc.jpg
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